Step 1

IIn a saucepan whisk together 3 egg yolks and 2/3 cups of sugar, then slowly add 1 cup milk continuously whisking and trying to dissolve the sugar and egg in the milk. Add 4 tbsp sifted cocoa and mix until fully incorporated and no cocoa streaks are seen. If you're having a hard time incorporating cocoa into the egg and milk mixture, run it through a sieve. Now set over medium and heat until the mixture thickens and coats the back of a wooden spoon. Do not stop whisking or the custard will scorch. Do not boil or the eggs will curdle and separate. You know the custard is cooked if you run your finger over the back of the dipped spoon and the streak stays clean, and no custard runs into it. Remove from heat and cool completely before adding to the butter mixture in the next step.

Step 2

With a mixer whip, 3 sticks room temperature butter for 5 minutes, or until whiter in color and fluffy. Scrape the sides of the bowl several times throughout the process to prevent chunks of butter being unwhipped.

Step 3

Add dulce de leche in two additions, whipping after each one to incorporate one.

Step 4

Then add the cooled chocolate custard in 2 additions until fully incorporated.

Step 5

Set aside until needed.

Step 6

With a whisk whip 7 tbsp room temperature butter for about a minute, add 2 whisked egg and thoroughly mix again. Mix 1 ½ cups sour cream with 1 tsp baking soda, then add it to the butter mixture. Add flour in two additions and mix until dough forms. Do not handle too much.

Step 7

Split the dough into 13-14 pieces and form balls. Cover the dough with plastic wrap and keep covered while you work with each dough ball.

Step 8

Roll two balls on a floured surface to a circle a bit bigger than a 8 inch round baking pan. Place two rolled out balls onto the back of the jelly roll sheet or a cookie sheet and bake in a preheated to 400°F oven until slightly golden in color, about 5-7 minutes. Repeat with the rest of the dough.

Step 9

As soon as the cake is baked place the 9 inch round baking pan on top of the cake and trim right around the pan. Discard the trimmings or crush and keep in a ziplock in the freezer for next time when you need to decorate the sides of the cake with something.

Step 10

While the cake layer is still warm put a dab of frosting on a plate, put the warm cake layer on top and add a generous spoon of frosting, spreading it around into an even layer. Reserve about 1/2 cup of frosting for covering the sides of the cake at the end.

Step 11

Continue baking the layers, trimming them and then stacking with frosting until all cake is baked and frosted.

Step 12

Cover the sides and top of the cake with reserved frosting, put a cake ring around the cake and secure it (if you have one). (The cake ring will help keep the sides straight and even as it sits. If you don’t have one, don’t worry about it, it’s not crucial). Cover with plastic wrap, then set a cutting board on top, next set something heavy on top of the cutting board to help the cake set. Let sit at room temperature for up to 24 hours before continuing.

Step 13

Make the chocolate whipped cream first: Next day whip together 1.5 cup whipping cream with 1/3 cup powdered sugar & 1-2 tablespoons sifted cocoa powder until fluffy and increased in volume. Use some of this frosting to cover the cake in a thin layer, smoothing out the top. Fit a ziplock bag with a large star tip. Fill the bag with leftover frosting. Pipe stars all along the border of the cake. Place a peeled hazelnut in the middle of each star. Dust the cake with powdered cocoa if desired.

Step 14

Cake is best served at room temperature.