GBBO Challenge with a Twist #1: Blackberry & Pistachio Mille-Feuille

Welcome to the newest feature on my blog, Great British Bake Off (GBBO) Challenges with a Twist! I decided recently that I am somewhat of a 'safe' baker. I tend to stick to baking things I know I am generally good at. Whilst doing this mostly produces good results for me (I say mostly because sometimes I'm not as good as baking certain things as I think I am and sometimes disasters are unavoidable no matter how skilled a baker you are) I realise that I'm not really stretching myself or widening my baking skill set by sticking to the 'safe' side.

So, in order to challenge myself and step outside of my baking comfort zone, I have decided to take on previous GBBO challenges and try to put my own little twist on them at the same time. The first instalment of this new feature begins with Blackberry and Pistachio Mille-Feuille.

The original GGBO challenge from series 6 episode 10 required finalist contestants to recreate Paul Hollywood's Raspberry Mille-Feuille, composed of layers of rough puff pastry, raspberry jam, Chantilly cream and fresh raspberries, topped with white and pink striped fondant. You can find Paul's original recipe HERE.

However, for me, Mille-Feuille is all about that delicious, creamy crème pâtissière and Paul's recipe lacked this. So, for my GGBO Challenge with a Twist, I decided to incorporate two flavours of crème pâtissière alongside Chantilly cream to produce some delicious, creamy (but not too sweet) slices of loveliness.

And I have to say, finishing these Mille-Feuille and marvelling out what I had somehow managed to produce without anything going seriously wrong was probably one of my proudest baking moments to date. These are delicious, even if I do say so myself. And SO worth the effort.

Though if you do make this recipe, make sure to take any Instagram-worthy photos before taking a bite, otherwise you will have nothing left to take photos of and that would be disappointing considering the effort that goes into this recipe.

Utensils: 3-4 baking trays (each at least 33cm x 25cm in size), non-stick baking paper, scissors, rolling pin, sieve, food processor or grinder, hand whisk, electric hand or stand mixer with whisk attachment, ruler, sharp knife, small palette knife, 4 disposable piping bags, 2-3 large round tipped piping tips (I used a Tala P6 tip but you could use any other piping tips of your choice) or one of these tips plus a coupler or two (to allow you to change the piping tip to a new filled bag easily).

Top Tip: Make sure your crème pâtissière is the right consistency before you start to pipe it. It should be a fairly thick, set custard. When spooned into a piping bag, it should not drip out of the end of the bag but should only come out when force is applied. If you are concerned your crème pâtissière is not thick enough, try piping a little bit onto a test puff pastry slice (see recipe for more information on the test slices). If the crème pâtissière is not able to hold its shape once piped, then it is not thick enough.

To thicken the crème pâtissière, place it back into a saucepan and in a separate bowl or cup, mix together 1 teaspoon to 1 tablespoon of cornflour with a small amount of water to create a smooth paste. The amount of cornflour you use will depend on how runny your crème pâtissière is; the runnier it is, the more cornflour you will need to use. Place the saucepan over a medium heat and slowly bring to the boil, whisking constantly. When the crème pâtissière is boiling, pour in the cornflour paste, still whisking constantly. As you do this, you should see the mixture start to thicken. Then, turn the heat down and allow the mixture to simmer for 1-2 more minutes, still whisking constantly. Finally, take the crème pâtissière off the heat and pour through a sieve (to room any lumps) into a bowl to cool. Cover the top with clingfilm to prevent a skin from forming and once cool, place in the fridge to set again before piping.

If after thickening your crème pâtissière now looks too set, use a hand or stand mixer with a whisk attachment to whisk the mixture to lighten it up. If needed, add a drop of milk to loosen the crème pâtissière up a little before placing in a piping bag and piping away.


Rough Puff Pastry

450g plain flour

Pinch of salt

75g butter, chilled and cut into small cubes

180g butter, frozen

Icing sugar for dusting

Crème Pâtissière

550ml whole milk

1 vanilla pod (split in half lengthways and scraped of seeds) or 1 teaspoon good quality vanilla bean paste

7 medium egg yolks

115g caster sugar

60g cornflour

Blackberry Purée

150g blackberries (reserve 6 of these blackberries for decoration)

30g granulated sugar

1 tablespoon water

Pistachio Paste

50g pistachios, shelled

25g ground or flaked almonds

20g granulated sugar

1/2 teaspoon almond extract

1 tablespoon water

Chantilly Cream

300ml double cream

25 icing sugar

1/4 teaspoon vanilla bean paste

Icing & Decoration

175g icing sugar, sifted

25g pistachios, shelled and finely chopped

6 blackberries (reserved from the 150g for the blackberry purée)

Pink shimmer sugar (or other decoration of your choice)

Makes:​ 6 Mille-Feuille slices (plus an extra half-formed test slice)


1. Make the rough puff pastry: For the pastry, mix the flour and salt together in a large mixing bowl. Rub in the chilled, cubed butter using your fingertips until the mixture resembles breadcrumbs. Gradually add enough water to form a dough. Paul's original recipe says you'll need about 4-6 tablespoons of water but I ended up using more like 8 tablespoons to be able to form a dough.

2. Tip the dough out of the bowl onto a lightly floured surface and knead the dough just a little to build up a bit of elasticity. Then roll the dough out into quite a long, portrait rectangle on a lightly floured work surface. For this next bit, have a watch of this video (starting at 0:40 seconds) as you go along.

3. Grate half of the frozen butter over the bottom two thirds of the dough. Then fold down the top third and fold up the bottom third as if folding a letter. Turn the folded dough 90 degrees to the right and then roll it out into a rectangle again.

4. Repeat the process of adding the remaining frozen butter to the bottom two thirds of the dough and then seal the edges of the folds so the butter doesn't all fall out. Then turn 90 degrees to the right and roll out into another rectangle. Finally, fold down the top third and fold up the bottom third one last time before wrapping the dough tightly in cling film and leaving to rest in the fridge for at least 30 minutes.

5. Make the blackberry purée: While the dough is chilling, weigh out 150g of blackberries and then reserve 6 of these blackberries for decoration. Place the reserved blackberries in a little pot or bowl and place back in the fridge for later. Place the rest of the blackberries in a small saucepan with the granulated sugar and water over a medium heat. Cook the blackberries until they start to release their juices (about 5-7 minutes) and then use a potato masher or spoon to crush the blackberries. Heat for a further minute before removing from the heat and pushing through a sieve into a small bowl. Set the liquid to one side to cool.

6. Make the pistachio paste: While the dough is still chilling, place the pistachios and ground or flaked almonds in a food processor (or something similar that will enable you to grind the nuts up) and pulse until the nuts are finely ground. Add the granulated sugar and pulse again to combine. Finally, add the almond extract and water and process until a smooth paste forms. Spoon the paste into a small bowl and set to one side.

7. Prepare the pastry sheets: Pre-heat the oven to 220°C (200°C fan) and line three large baking trays (mine were 36cm x 25cm in size) with non-stick baking paper. Divide the pastry into three equal pieces and roll each piece to a 30cm x 23cm rectangle, about 5mm thick. Place each pastry sheet onto the lined baking trays, and place back in the fridge for 10-15 minutes.

8. Bake the pastry sheets: Remove the chilled pastry sheets from the fridge and dusty each one heavily with icing sugar using a sieve. Then place a sheet of non-stick baking paper on top of each pastry sheet and place another baking sheet on top before placing in the oven. As I had four trays, I baked two pastry sheets in one session and one pastry sheet in the second session.

9. Paul's original recipe says to bake the pastry sheets for 10-15 minutes until golden-brown and crisp, however I ended up baking my pastry sheets for 15 minutes with the trays on top and then a further 5 minutes with the trays and baking paper removed. Remove from the oven and set aside to cool.

10. Make the crème pâtissière: Place the milk and vanilla seeds or vanilla bean paste in a small saucepan and warm until tepid. In another heavy based saucepan, whisk together the egg yolks, sugar and cornflour using a hand whisk until smooth and pale.

11. When the milk is tepid, slowly whisk the milk into the egg mixture and then place on a medium heat. Whisk the mixture vigorously until it starts to thicken and comes to the boil. Continue to whisk for a further 1-2 minutes and then pass the mixture through a sieve into a bowl.

12. Flavour the crème pâtissière: While the crème pâtissière is still warm split it evenly into two separate bowls. Add 3-4 tablespoons of the blackberry purée to one bowl and all of the pistachio paste to the other bowl and mix both bowls well to combine. Cover the bowls with cling film, placing the cling film in contact with the top of the crème pâtissière to stop a skin from forming, and set to one side to cool. Once cool enough, place both bowls in the fridge to set.

13. Make the Chantilly cream: Using a hand or stand mixer with whisk attachment, whisk the cream, icing sugar and vanilla to soft peaks. Place in the fridge for later.

14. Cut pastry slices: When the pastry has cooled cut six 12cm x 5cm rectangles of pastry from each sheet of baked pastry so that you have 18 pastry slices. When I cut mine, I managed to get 20 pastry slices out of my pastry sheets, so I used my two extra slices as test slices to make sure the crème pâtissière was thick enough to pipe and the icing was the right consistency for the tops of the slices.

15. Make the icings: In a small bowl mix together 25g of sifted icing sugar with 1 tablespoon of blackberry purée. Place in a disposable piping bag and set aside. In another bowl add 150g of sifted icing sugar and gradually stir in water, 1 tablespoon at a time until you have a thick but just about pourable consistency.

16. Ice your top pastry slices: Lay 6 of your best-looking pastry slices out on a cooling rack plus one of your extra test slices. Spoon a small amount of white icing over your test slice to check the consistency. The icing should be spreadable and may drip a little off the sides of the pastry, but shouldn't be so thin that it runs off completely. Once you are happy with your consistency (add a little more icing sugar or water until you reach the right consistency if needed), spoon the icing over the remaining 6 slices and spread using a small palette knife to ensure the icing covers the whole slice.

17. Next, before the white icing sets, snip the very end off the piping bag containing your blackberry icing so that you only have a very small hole. With each pastry slice in portrait format, pipe a series of horizontal lines on the top of each slice (I think I piped about 7 blackberry lines per slice) and then drag a cocktail stick or the back of a knife vertically through the horizontal lines, alternating dragging the cocktail stick up and down through the lines. Place the pastry slices in the fridge to set.

18. Prepare and fill your piping bags: For this bit you'll need 3 disposable piping bags and 2-3 large round tipped piping tips (I used a Tala P6 tip but you could use any other piping tips of your choice) or one of these tips plus a coupler or two (to allow you to change the piping tip to a new filled bag easily). Fit each piping bag with a piping tip and / or coupler and fill one piping bag with Chantilly cream, the second with blackberry crème pâtissière and the third with pistachio crème pâtissière. Make sure to check the consistency of your crème pâtissière before piping. It should be a fairly thick set custard. When spooned into a piping bag, it should not drip out of the end of the bag but should only come out when force is applied. If you're worried your crème pâtissière is not the right consistency see the top tip at the top of this recipe.

19. Assemble the mille-feuille: Lay out 6 pastry slices plus your remaining extra test slice on your work surface or a large chopping board. Starting with your test slice to check the consistency of your crème pâtissière, pipe 8 Chantilly cream dots around the edge of the rectangle (4 dots along each long edge). Next, swap to the blackberry crème pâtissière and pipe dots of this in the gaps between the cream and in the middle of the rectangle. Repeat this process for your 6 remaining slices.

20. Place 6 more pastry slices on top of your piped slices and then start the process again by piping 8 Chantilly cream dots around the edge of the rectangle (4 dots along each long edge). This time, swap to the pistachio crème pâtissière and pipe dots of this in the gaps between the cream and in the middle of the rectangle.

21. Place the iced pastry slices on top of each piped pastry slice. At one end of each iced slice, use a dot of Chantilly cream to secure a blackberry on top. Finish the mille-feuille by sprinkling the top with chopped pistachio and pink shimmer sugar (or other decorations of your choice).

22. Take lots of pictures of your beautiful creations!

Storage: Store in an airtight container in the fridge for up to 3 days. Keep any leftover rough puff pastry bits, crème pâtissière and Chantilly cream for a cheeky dessert version of crisps and dip.

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