Ingredients

5 large egg yolks

2/3 cup granulated white sugar (divided into 1/3 cup + 1/3 cup)

7 tablespoons potato starch

2 1/2 cups whole milk

1/4 teaspoon salt

2 teaspoons pure vanilla extract

2 teaspoons vanilla bean paste (or more vanilla extract)

200 grams unsalted butter (at room temperature; about 14 tablespoons + 1 teaspoon)

2 tablespoons granulated white sugar

3/4 cup water

6 tablespoons unsalted butter

1/8 teaspoon salt

3/4 cup all-purpose flour

3 large eggs

1 large egg yolk

Butter (to grease the pans)

Powdered sugar (for dusting on top)

Instructions

Step 1: Make the Crème Pâtissière by beating egg yolks with 1/3 cup sugar until thick and pale yellow. Add potato starch and mix well.

Step 2: Heat milk, remaining 1/3 cup sugar, and salt in a saucepan until gently simmering. Remove from heat.

Step 3: Gradually whisk 1 cup of hot milk into the egg yolk mixture, starting with a few drops. Pour mixture back into the saucepan, add vanilla extract and vanilla bean paste, and cook over low heat whisking constantly until thickened, about a minute.

Step 4: Transfer custard to a bowl, cover with plastic wrap touching the surface, and cool to room temperature.

Step 5: Preheat oven to 380°F. Line the bottoms of two 8 or 9-inch springform pans with parchment paper and grease the sides with butter.

Step 6: For the choux pastry, melt butter in water with salt over medium heat. Remove from heat, add flour all at once, and return to low heat, stirring constantly until dough forms a ball and leaves residue on the pan bottom (about 2 minutes).

Step 7: Transfer dough to a bowl, let cool slightly (warm but not hot), then beat in eggs and egg yolk one at a time with an electric mixer until smooth and glossy.

Step 8: Divide dough between pans and spread roughly to create peaks and divots, mimicking mountain shapes.

Step 9: Bake choux cakes until puffed and golden, about 25–28 minutes. Cool for 10 minutes in pans, then remove and cool completely on a wire rack.

Step 10: Finish Crème Mousseline by creaming butter and 2 tablespoons sugar until pale and fluffy. Beat in custard a spoonful at a time until fully combined and the mixture is light and fluffy.

Step 11: If cakes are not fully cool, cover the mousse with plastic wrap to keep fresh.

Step 12: Assemble the cake by placing one choux cake in a springform pan, spreading the crème mousseline evenly on top, then layering the second cake over it.

Step 13: Refrigerate for 1 hour before serving. Remove from pan and dust the top with powdered sugar just before serving.

Tips & Variations

Use vanilla bean paste for a more intense vanilla flavor, or increase vanilla extract if you don’t have paste.

Allow the custard to cool completely before mixing with butter to prevent melting the butter and losing fluffiness.

Create the uneven peaks on top of the choux pastry to give Karpatka its signature mountain-like appearance.

FAQs

Can I use a different starch instead of potato starch?

Yes, cornstarch can be used as a substitute, but potato starch gives the custard a smoother and silkier texture typical of Karpatka.

Can Karpatka be made ahead of time?

Karpatka can be assembled a day ahead and stored in the refrigerator to allow the flavors to meld. Just dust with powdered sugar right before serving for freshness.