Polish Vanilla and Raspberry Ripple Custard Slice (Karpatka)

Mille-feuille, the classic french pastry. Just the word puts a shiver down my spine.  I'm no trained pastry chef and I think others would agree with me in saying that this is one of the hardest things to perfect - looks wise! I can never quite master the uniformity aspect, some custard always manages to seep its way out the sides either in cutting or by overfilling!  

Other than the hard to pronounce mille-feuille, there are many names it can also answer to, vanilla slice, custard slice, or even Napoleon. However, Karpatka is one that doesn't normally get used. After a bit of quick googling I found that there aren't that many english recipes out there for the polish variation, proving that it is still very much under the radar in this country and as a result not many people even know what the difference is between the french and polish. 

The clue is hidden in the name! Only you need to be able to speak Polish to understand... Karpaty is a mountain range (Carpathian Mountains) in Southern Poland. The vanilla custard cream is sandwiched between layers of choux pastry instead of puff and once cooled, it forms many ridges creating the characteristics similar to those in the Polish mountain valleys.

I've put my take on the traditional recipe by rippling in crushed raspberries to give a vibrant pink colour burst swirled into the light and airy, pale vanilla pastry cream. The berries also gives a bit of tart - pucker your lips - sweetness which is needed along with a good dredging of icing sugar. Don't be shy with a big dusting of the white stuff since there isn't much sugar elsewhere apart from in the custard. 
Note: Store the slices in the fridge and consume within 2 days. Bring them to room temperature before serving. You may need to re-dust with some icing sugar.
 

Polish  Vanilla  and  Raspberry  Ripple  Custard  Slice (  Karpatka )

Ingredients:

For the choux pastry: 125g (1/2 cup) unsalted butter, extra for greasing 240ml (1 cup) water  120g (1 cup) plain flour 5 eggs
For the filling: 375ml ready-made fresh custard 1 egg 1 tbsp vanilla extract 2 tbsp plain flour 1 tbsp cornflour (cornstarch) 150ml thickened cream 150g (about 1 + 1/4 cup) fresh raspberries
To serve:  Icing sugar

Method:

Preheat the oven to 220°C/ 200°C fan/ 425°F / gas mark 7. To make the choux pastry, in a saucepan bring the water and butter to the boil, then add flour and mix vigorously with a wooden spoon until the mixture comes away from the sides and forms a ball keeping it on the heat for a minute to cook out the flour. Transfer the dough to a mixing bowl and leave to cool for about 5 minutes.
Add the eggs to the dough one at a time, beating with an electric mixer after each addition until glossy and smooth. Grease a large baking tray at least 20 x 30 cm in length and line with non-stick baking paper, then grease. Spread the pastry into a rough rectangle until the dough is only a couple of centimeters thick. Place in the oven and bake for about 30-40 minutes, until the pastry is golden brown on top, crisp and the bottom has dried out, if the inside looks a bit wet still then turn down the oven temperature slightly and cook for longer.  
Remove from the oven and leave to cool completely on a wire rack. Meanwhile make the pastry cream, in a large saucepan, combine custard, eggs, flour, cornflour and vanilla extract. Whisk until smooth. Place over low heat and cook, whisking, until the custard thickens. Transfer to another bowl and leave to cool to room temperature, whisking from time to time to prevent the skin from forming.
Whip the cream so it's thick and forms peaks, then fold slowly into the cooled custard mixture. Crush the raspberries in a small bowl, almost to a coulis consistency. To assemble the karpatka, cut the edges of the choux pastry sheet so you have a straight sided rectangle. 
Cut the long side of the rectangle in half, the two smaller rectangles will now be the top and bottom layer. Spread over the pastry cream, leaving a 2cm gap around the edge. Add the crushed raspberry mixture on top of the pastry cream, spreading to cover the pastry cream layer. Sandwich together with the remaining choux pastry rectangle. Cut into 8 equal sized pieces. 
When ready to serve, dust with a generous amount of icing sugar.