Ingredients

2 ½ cups milk

150 grams (¾ cup) granulated sugar

½ teaspoon kosher salt

50 grams (5 tablespoons) cornstarch

4 large egg yolks

2 teaspoons pure vanilla extract or vanilla bean paste

¾ cup water

85 grams (6 tablespoons) unsalted butter (at room temperature)

¼ teaspoon kosher salt

95 grams (¾ cup) all-purpose flour

3 large eggs

200 grams (14 tablespoons) unsalted butter (at room temperature)

25 grams (2 tablespoons) granulated sugar

Butter (for greasing pan)

Confectioners’ (powdered) sugar (for topping)

Instructions

Step 1: Make the crème pâtissière. Heat the milk, half the sugar, and salt in a saucepan over medium heat until simmering, not boiling. In a separate heat-proof bowl, whisk the remaining sugar and cornstarch, then stir in the egg yolks until smooth.

Step 2: Temper the egg yolks by gradually whisking in about ½ cup of the hot milk mixture. Pour the tempered egg mixture back into the saucepan with the remaining milk. Return to medium-low heat and whisk until thickened, about 5 to 9 minutes. Remove from heat and stir in vanilla. Cover with plastic wrap pressed to the surface and cool to room temperature.

Step 3: Prepare the pâte à choux. Preheat oven to 400°F (200°C). Grease two 9-inch springform pans and line the bottoms with parchment paper. In a medium saucepan over medium heat, melt butter with water and salt. Remove from heat and stir in flour all at once.

Step 4: Return the pan to medium-low heat and cook, stirring constantly, until the dough forms a ball and leaves a film on the bottom, about several minutes. Transfer dough to a mixer bowl and cool 10 minutes. With the mixer running, add eggs one at a time until smooth and glossy.

Step 5: Divide dough between pans. Spread unevenly to create peaks and divots, mimicking mountain shapes. Bake 24 to 28 minutes until puffed and golden. Cool in pans 10 minutes, then on wire racks completely. Repeat for second layer if needed.

Step 6: Make the crème mousseline. Beat room temperature butter and sugar until pale and fluffy. Loosen the cooled pastry cream in its bowl, then gradually add it to the butter mixture while mixing on medium-low. Continue beating until light and fluffy, about 5 minutes. Cover and keep at room temperature until assembly.

Step 7: Assemble the Karpatka. Place a springform ring on a serving plate, optionally lining edges with parchment paper. Put the less puffed choux layer inside, spread custard evenly over it, then top with the second choux layer.

Step 8: Refrigerate at least 1 hour, up to 3 hours, to set the filling. Remove the ring and parchment paper. Dust the top generously with powdered sugar before serving.

Tips & Variations

Use vanilla bean paste for a richer, more intense vanilla flavor in the custard.

Make sure butter and pastry cream are at the same room temperature before mixing to ensure a smooth, creamy filling.

If you only have one springform pan, bake the choux dough in two separate batches, allowing layers to cool before assembling.

Create the characteristic peaks by spreading the dough unevenly with the back of a spoon before baking.

FAQs

Can I make Karpatka ahead of time?

Yes, you can prepare the pastry and cream in advance and assemble the cake a few hours before serving. Keep it refrigerated until ready to serve for the best texture and flavor.

What can I substitute for cornstarch in the custard?

You can use all-purpose flour as a thickener, but use double the amount and be aware the texture may be slightly less smooth. Alternatively, tapioca starch can be used in equal amounts to cornstarch.