Make cookie dough first. Wash your hands thoroughly, just simple soap and water. Separate the egg yolks from the egg whites. Put flour on a board, then cut and rub in the frozen butter. When the butter chunks are small and rubbed into the flour (like nokedli egg-drop noodles for soup), make a hole in the middle of the flour and crumble in the yeast. Mix the yeast thoroughly with the butter flour mix.

Add egg yolks, and by hand, mix by squeezing the yolks throughout the flour/butter/yeast. (This is messy but it works!) Add the sour cream, and continue to hand mix thoroughly. Work the dough until it is uniform in color and looks like one homogenous mass. The dough can finally be formed into a roll of constant diameter, then cut into 4 equal pieces. Store the dough in the refrigerator while preparing the filling.

Beat the egg whites until stiff. This can be done with a dinner fork, or (recommended), with a machine. Mix ground walnuts and sugar together. Add stiff egg whites slowly while mixing. Add brandy.

Remove one section of dough from the refrigerator. Roll it out until it is about 1/8 inch thick. Then take it up and form a ball! Reroll the dough out a second time to less than 1/8 inch thick. Cut into squares 2 inches on a side, putting the trim pieces into another ball. Roll each cut 2 x 2 square, to about a 2 1/2 inch square to achieve a final thickness of about 1/16 inch. (This is the part that takes the most practice to develop the necessary skill, and determines the form of the cookies after baking.) Trim the square to 2-1/2 inches and put the trimmings into the dough ball.

Place filling in center of square (not too much!) and fold dough diagonally over it. Push the edges of the resulting triangle together. Roll up the triangle from the diagonal to the tip. With the tip on the bottom, sharply bend the dough with the filling inside so that the ends nearly touch. This takes a lot of time to do properly, but the results are worth it visually. Do the same with the ball of dough you have been collecting, then repeat the process with the 3 remaining pieces of dough in the refrigerator. With practice, you will use up all the ingredients.

Test bake a few cookies to find out if your forming of the cookies is correct. Place the formed cookies on an aluminum cookie sheet that has been dusted with flour. Bake in a pre-heated oven at 350°F for 15 to 20 minutes. When the cookies start to turn a slightly brownish yellow take them out. Sprinkle with powdered sugar. Usually the cookie dough thickness and forming process requires a few tries to get it right. As the cookies bake, the dough will thicken, the filling will expand and the cookie ends will stretch out. Properly formed cookies will show the filling at the ends after baking, but not too much.

These cookies taste best after a couple days in a cookie tin, letting the flavors mingle. They hold their flavor well and can be frozen for future delight. For maximum flavor, serve the cookies at room temperature or slightly warm. Now you know why making these cookies is a labor of love.