Prepare the Cream Filling: In a medium saucepan, whisk together 2 eggs and 150 grams of sugar until smooth.

Gradually add 70 grams of cornstarch and mix until well combined.

Slowly pour in 500 grams of milk, stirring continuously to avoid lumps.

Place the saucepan over medium heat and cook, stirring constantly, until the mixture thickens and comes to a gentle boil.

Remove from heat and add 50 grams of butter and vanilla sugar. Mix until the butter melts and the cream is smooth. Set aside to cool.

Prepare the Pastry Dough: In another saucepan, bring 180 grams of water, 90 grams of butter, a pinch of salt, and a pinch of sugar to a boil.

Remove from heat and add 130 grams of flour all at once. Stir vigorously until the dough comes together and pulls away from the sides of the pan.

Let the dough cool slightly before adding eggs, one at a time, mixing thoroughly after each addition until the dough is smooth and glossy.

Transfer the dough to a piping bag fitted with a large round tip.

Pipe the dough onto a baking sheet lined with parchment paper, creating 2–3 layers to form discs of about 18 cm in diameter.

Bake in a preheated oven at 190°C (375°F) for 30 minutes or until golden brown. Set aside to cool.

Prepare the Sour Cream Layer: In a mixing bowl, combine 500 grams of sour cream, 150 grams of sugar, 2 tablespoons of cornstarch, 8 grams of vanilla sugar, and 2 eggs.

Pour the mixture into a saucepan and cook over medium heat, stirring constantly, until it thickens to a custard-like consistency.

Remove from heat and add 50 grams of butter, stirring until melted and fully incorporated. Set aside to cool.

Prepare the Pastry Crust: In a large bowl, mix 250 grams of flour, 70 grams of powdered sugar, and 150 grams of cold, cubed butter.

Use a pastry cutter or your fingertips to blend until the mixture resembles coarse crumbs.

Divide the dough into two parts, wrap each in plastic wrap, and refrigerate for 30 minutes.

Roll out each portion to about 18 cm in diameter and bake in a preheated oven at 190°C (375°F) for 10-15 minutes or until golden brown. Let them cool completely.

Assemble the Cake: Place one of the baked pastry discs on a serving plate and spread a layer of the cream filling on top.

Add another layer of the baked pastry disc and repeat the process, alternating between the sour cream layer and cream filling until all layers are stacked.

Cover the cake with plastic wrap and refrigerate for at least 6 hours or overnight to allow the flavors to meld together.

Decorate and Serve: Melt white chocolate and drizzle it over the top of the cake or use it to create elegant swirls or patterns.