Karpatka Cake

Directions

1. In a large saucepan, combine milk, 1/2 cup sugar and salt. Heat over medium until barely simmering. In a large bowl, whisk together egg yolks, 1/4 cup sugar and cornstarch until smooth. Reduce heat to medium-low; whisk 1/2 cup of the warmed milk mixture into the egg yolk mixture, whisking vigorously to avoid curdling. Transfer all the egg yolk mixture to the saucepan. Continue cooking over medium-low heat, whisking constantly until thickened, 7-10 minutes. Immediately remove from the heat; stir in vanilla extract. Transfer to a glass bowl; cover with plastic wrap. Let cool to room temperature.
2. Once cooled, in the bowl of a stand mixer, beat together softened butter and the remaining 3 tablespoons sugar until pale, 2-3 minutes. On medium-low speed, gradually mix in the pastry cream, one spoonful at a time until well-combined and fluffy. Cover; set aside.
3. Meanwhile, preheat the oven to 400°. Butter the sides and base of two 9-in. springform pans; place a circle of parchment paper in the bottom of each; set aside.
4. In a large saucepan over medium heat, add water, butter, sugar and salt. Allow the butter to melt. Remove the saucepan from the stove; vigorously stir in flour until incorporated. Place the saucepan back on medium-low heat. Continue cooking until the moisture is out of the dough and a white film is visible on the bottom of the pan, 5-7 minutes. Transfer to a stand mixer fitted with the paddle attachment. Let cool 15 minutes. Once cooled, beat in eggs, one at a time, until fully incorporated.
5. Divide the dough into the prepared springform pans. Use the back of a spoon to create uneven swirls. Place the springform pans on a baking sheet. Bake 25-30 minutes or until the tops are golden brown. Turn the oven off; leave the cakes in the oven for an additional 10 minutes. Remove; let cool completely.
6. Line another 9-in. springform pan with a ring of parchment paper. Place one cake layer in the bottom. Spread the pastry cream filling on top. Place the remaining cake layer on top of the filling, pressing down gently. Cover the pan with plastic wrap. Chill at least 2 hours. To serve, dust with confectioners' sugar; slice into wedges.