For the test, divide the egg and beat the yolk with 1/3 of the sugar until white, and the protein with the rest to solid peaks.
Mix cottage cheese with sour cream until smooth. Add room temperature oil and beat with a mixer. Add whipped yolk in the process. Then add flour with baking powder, mix well, it is better to add flour in portions so that the dough is not very thick. Then add the protein and mix again.
Lubricate the baking dish with butter and lay out the dough leaving a little room for raising. Lay out the dough and bake at 180 degrees until golden brown, about 15-20 minutes.
For cream, beat the protein with sugar in a water bath until solid peaks.
Pull the cupcakes from the mold, let it cool slightly and put the jam in the middle. Squeeze out a ready-made protein cream using a pastry bag.
Katyusha cake is ready, you can serve immediately.