Pour cold butter into the flour, rub the flour into a creamy crumb. Add the yolks to the crumbs, add salt and sour cream, and knead a soft and sticky dough.

Divide the dough into 30 pieces, form balls. Cover the balls with cellophane and send to the freezer for 30 minutes.

Pour sugar, vanilla sugar and corn starch into a bowl with egg whites, pour in citric acid. Beat the whites with a mixer to a white glossy mass.

We roll the cold balls into thin cakes, where we put a teaspoon of the filling.

Seal the filling inside the cakes, close the opposite ends together.

We spread the cookies on a sheet covered with parchment. Bake cookies at 200 degrees for 10 minutes.

You can also add walnuts to the filling for a more interesting taste.

After cooking, the shells should be sprinkled with powdered sugar.

Ingredients for the dough:

• Flour – 380 g;
• Butter – 200 g;
• Egg yolks – 4 pcs.;
• Salt – 1/3 tsp.
• Sour cream – 100 g.

Ingredients for the filling:

• Egg whites – 4 pcs.;
• Sugar – 200 g;
• Vanilla sugar – 8 g;
• Citric acid – a pinch;
• Corn starch – 2 tsp.