Place flour in a mixing bowl. With a pastry blender or 2 knives, cut in butter or margarine till mixture resembles small peas. Stir in the sour cream and vanilla just till dough holds together. On a lightly floured surface, knead dough about 10 times. Divide dough in thirds. Wrap in plastic wrap.
On a lightly floured surface, roll one third of the dough into a 10-inch circle. Spread dough with a scant 2 tablespoons of the preserves or marmalade. Sprinkle with one third of the chopped white baking bar. Cut dough into 12 wedges. Starting at curved edge, roll up each wedge jelly-roll style. Place, point-side down, 2 inches apart on an ungreased cookie sheet. Repeat with remaining dough, preserves or marmalade, and white baking bar.
In a small mixing bowl stir together the sugar and, if desired, cinnamon; sprinkle over each cookie.
Bake in a preheated 375 degrees oven for 20 to 25 minutes, or till light golden brown. Remove cookies from pans and cool on a rack. Store in a tightly covered container.
Makes about 36 cookies.
Date: October 31, 2002