First, let's deal with the cakes. To knead the dough, you need to grind eggs with sugar + vanilla, pour in kefir, add flour with slaked soda and mix. In the presence of a mixer, it is better to beat everything in the same order.
Divide the dough into two parts. Add cocoa to one and knead, and leave the other as is. If desired, cocoa can be added to both parts. In this case, the cake will turn out with a richer cocoa flavor.
Now, it remains just to pour the dough into forms greased with oil or covered with parchment. Bake for 20 minutes at 200 degrees. Readiness is checked with a wooden splinter.
We take out the finished cakes from the mold, cool and cut one of the cakes into cubes (3x3 cm).