Step 1. Preparation of the dough. Butter chop with flour. Separate the yolks from the whites. Add egg yolks, sour cream, powdered sugar, salt and soda, quenched with vinegar or lemon juice. All knead well. The dough should move away from the hands. Ready dough put in the fridge for 30 minutes. Take out, knead again and put into the refrigerator for 30 minutes. After divide the dough into 30 balls and put them in the freezer for another 30 minutes.

Step 2. Prepare the filling. Whisk the whites to a thick foam. Then gradually add powdered sugar, continue whisking. In the obtained mass add the crushed walnuts. All mix well.

Step 3. Cooking. Ball out thinly.

Step 4. In the center put the filling.

Step 5. Roll twice in half.

Step 6. Bake at t 200°C for 25-30 minutes.

Step 7. Sprinkle ready brownies with icing sugar.