• Set your oven to a warm 200C/390F. Line two 23cm/9-inch springform tins with parchment and brush the sides with oil or butter.

DOUGH MIXTURE

• In a saucepan, blend together water, milk, butter, sugar, salt, and vanilla. Warm this blend over a medium heat until it just begins to bubble.

Mixing in the flour

• Once off the heat, whisk in the flour till thoroughly combined. Return to a low heat, stirring until the dough forms a singular mass with a light film forming underneath.

Cooling and egg incopororation

• Remove the dough to a mixer, letting it sit to cool for ten minutes. One by one, beat each egg in until the mixture is smooth and cohesive.

Dividing and baking the dough

• Distribute this dough into your two prepared tins. No need to be levelled out this unevenness will create random bubbles on the surface of the cake layers during the baking, which represent the Carpathian mountains.
• Place in the oven to bake for 25-30 minutes, looking for a rich, golden brown shade. Leave to cool in the tin for 10 minutes then let it cool off completely on a wire rack before moving on to your next steps.

CREAMY FILLING

• Warm up milk, a portion of the sugar, and pinch of salt in a saucepan until it simmers.

Combining Yolks and Dry Ingredients:

• Whisk the remaining sugar with cornflour, egg yolks, and more vanilla in a separate bowl.
• Ensure you reach a smooth texture without any lumps.

Tempering and Cooking the Cream:

• Slowly pour in half of your heated milk to the yolk mix, whisking constantly to blend.
• Transfer this combined mixture back to the remaining milk in the saucepan.

Thickening the Pastry Cream:

• Gently heat this blend until it thickens into a custard, for 5-7 minutes.
• If any lumps form, beat them out until they're seamlessly dissolved.

Cooling the Pastry Cream:

• Once off the heat, pour this cream into a flat dish.
• Overlay it with cling film making sure there's no air in between and cool till it's room temperature.

Creating Mousseline Cream:

• Whisk the softened butter and a spoonful of sugar until it's pale and airy. Set aside
• Revive the chilled pastry cream with a brisk whip to smooth any stiffness.

Finalising the Filling:

• Introduce your pastry cream gradually into the butter, whisking at a medium pace after each addition, until fully blended.
• Scrape the edges and give one final spin for 10 seconds.

Assembly and Setting:

• Proceed with layering your Karpatka cake. Using a springform tin line the sides with baking paper and place one layer of the baked cake on the base. Press down slightly then add the cream. Top with the other layer and allow it to set in the fridge for 2 - 3 hours.
• Just before serving, grace with a light dusting of icing sugar.