Turn on the oven to preheat.

Beat the egg yolks into a fluffy foam with sugar and vanilla. This usually takes about three minutes.

Add sour cream and softened butter to the beaten egg yolks (the butter should be at room temperature; you can melt it slightly in the microwave on the "defrost" setting if it is cool in your home, but under no circumstances should you melt it completely to a liquid state).

Then gradually add the sifted flour, baking soda, and salt, and knead into a soft, smooth dough.

The dough will become soft and sticky to the hands, so it is best to place the cookies on a baking sheet using a pastry bag and a nozzle.

It is better to choose a wide nozzle so that the dough comes out easily under pressure.

Place the cookies on a baking sheet lined with parchment paper.

If you plan to make cookies with jam, then after depositing the dough, you need to carefully make indentations for the jam. This is easy to do with a slightly damp finger or a Japanese cooking stick. Then put a little jam in the indentations. It can also be added from a pastry bag.

Bake the cookies at a temperature not exceeding 180 degrees in "convection" mode for about 10 minutes.

When the cookies are golden brown, remove them from the oven and let them cool.