Karpatka cake, the Polish dessert that everyone will love

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Ingredients:
For the 2 bases:
100 gr of flour
120g of water
70g butter
3 eggs
salt
4 g of yeast
Cream:
500 ml of milk
140 g of sugar
10 g of vanilla sugar
40 grams of cornstarch
2 eggs
180 gr of soft butter
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Preparation
Base:
Place the flour, water, butter, salt and baking powder in a saucepan and bring to the heat. When the dough comes away from the bottom, transfer it to another bowl and add the eggs. Place the dough in two 25 cm molds and bake at 400°F (200°) for 20-30 minutes.
Cream:
Mix the eggs with a little milk and starch, set aside. Bring the milk, sugar and vanilla sugar to the heat. Once boiling, pour the milk into the mixture with the eggs. Return to the heat and let thicken. Whisk the butter and add it to the cream, stuff the two bases and serve.