Alla's Cookies

First, cut the well-chilled butter into the flour until it resembles a fine crumb.

Next, transfer the crumbs to a bowl, add salt, egg yolks, and sour cream, then knead into a smooth, non-sticky dough.

Divide the dough into three portions, wrap each in plastic wrap, and refrigerate for 30 minutes.

Meanwhile, prepare the filling: grind the walnuts using a meat grinder or pulse them in a food processor.

Whip the egg whites into stiff peaks, then gently fold in the sugar and ground nuts.

Grease a baking sheet with butter. Take one portion of dough, roll it out thinly to fit the baking sheet, and transfer it over.

Spread half of the filling evenly over the top.

Roll out the second layer of dough, place it over the filling, spread the remaining half of the filling on top, and cover with the third dough layer.

Brush the surface of the pastry with an egg yolk mixed with a little water.

Before baking, cut everything into diamond shapes: slice parallel lines along the long side about 3 cm apart, and then cut diagonally from the start of each line.

Place the baking sheet in a preheated oven at 180°C (350°F) and bake for about 35 minutes until golden brown.