The Following recipes are from The Frugal Gourmet Celebrates Christmas, which is a beautiful book.

Combine the flour and salt in a mixing bowl. Cut in the butter until grainy. In a small bowl, combine the sour cream; egg yolks and lemon juice. Blend the sour cream mixture into the flour mixture. Knead together to form a smooth dough. Place the dough on plastic wrap and pat it into a 6 x 8-inch rectangle. Wrap and refrigerate 2 hours, or overnight.

filling: Whip the egg whites until stiff but not dry. Gradually whip in the sugar to form a meringue. Whip until the meringue holds soft peaks. Fold in the remaining ingredients. Dust a rolling pin and the counter with flour. Roll the chilled dough out into a thin (1/8-inch maximum) rectangle on the floured counter. Trim the edges so the rectangle measures 24 x 15-inches. Cut the dough into 3-inch squares and dust with confectioners' sugar. Place a rounded teaspoon of the filling in the center of each dough square. With a tiny bit of water, dampen two opposite corner. Fold the two opposite corners over each other and press the center together lightly. Place the cookies on a nonstick baking sheet and bake in a preheated 350 oven for 30 minutes, or until lightly browned.