In a bowl, stir together the flour and yeast. Cut in the cold butter with pastry blender or two knives, until the mixture resembles coarse meal. Stir in the egg yolks and sour cream and combine well.
Form the dough into a ball, wrap in plastic wrap, and chill in the refrigerator overnight.
The next day, preheat the oven to 350°F. Grease a cookie sheet. Mix walnuts and chocolate chips in a medium bowl. Set aside. Remove dough from refrigerator and quarter the dough, forming each quarter into a ball.
On a floured surface, roll one ball of dough into a rectangle. Spread a thin layer of raspberry jam over the dough. Sprinkle 1 quarter of the walnut mixture on top of raspberry jam. Fold in the edges and roll dough to the end; place on prepared cookie sheet.
TOPPING
Mix cinnamon and sugar in a small bowl. Brush top of pastry with melted butter and sprinkle with 1 quarter of the cinnamon/sugar topping mixture.
Bake for 15 minutes, or until golden brown. Remove from oven; let sit for 10 minutes. Then slice into 1-inch slices on the diagonal.
Repeat above steps with remaining 3 balls of dough.