Soften butter. Mix with flour and add sour cream and egg yolk. Work into a ball. Then divide the ball into 4 smaller balls. Refrigerate for 4 hours or more. Then roll one ball out like a pizza, 0 cm thick. Sprinkle cinnamon, sugar and chopped nuts over the dough. Cut into 16 pieces like a crescent roll and roll up. Bake at 180ºC for 25 minutes. ----