How to make Smetannyk:

For the sponge:

• Preheat the oven to 356°F/ 180 °F.
• The Smetannyk cake is made using 2 different sponges: a light colored one and a dark one. You can prepare these individually (in case you have just one baking tray, for example - simply halve the quantities of each ingredient used and make each batter one at a time), but to keep things simple and speed up the baking time, we'll make one big batch of sponge batter and divide them into 2 baking trays before placing them in the oven.
• So, to start with, add the sour cream and the butter in a bowl and mix them together until well combined. Then, add in the eggs and the sugar and baking soda and whip everything well, until the sugar has mostly dissolved.
• Then, mix in the flour until the mixture is homogenous and lump-free. You should get a smooth batter - not too thick (like a yeast dough), but not too thin either.
• Line your baking trays with parchment paper. Pour half the amount of sponge batter into one of the baking trays/moulds. Add the cocoa powder to the remaining batter in the bowl, and mix well until the color is even, then pour it into the other tray.
• Place in the oven and bake for 15-35 minutes (baking time varies depending on your oven and the thickness of each sponge cake, so check for doneness regularly using the toothpick method).
• Once done, take the sponge cakes out of the oven, transfer to a cooling rack and let them cool down fully.

For the cream:

• While the cakes cool down, add the sugar and the sour cream to a bowl and whisk until the sugar has fully dissolved. Put the cream in the fridge until it's time to assemble the cake.

Assembly:

• Carefully cut each of the sponge cakes into halves (2 layers each).
• Spread some cream on the top of one half of the light-colored sponge, then add a colored layer on top, followed by another layer of cream and so on, until you finish with a final layer of cream on top.
• Don't forget to spread the cream around the sides of the Smetannyk cake, as well!
• Place the cake in the fridge and leave for 6-8 hours or overnight. This is to allow the cream time to firm up, and soak into the sponge.

Enjoy!