Pour flour in a mixing bowl and with a pastry cutter cut in the butter or margarine till the mixture resembles small peas. Stir in the sour cream and vanilla till the dough holds together. Place it on a lightly floured surface and start kneading for a couple of minutes. Divide the dough into 3 pieces and wrap in plastic wrap.
Roll one piece of the dough at a time into 12 inch (30 cm) circle. This is like making pizza. Spread the dough with 2 tbsp of jam and sprinkle with one third of the chopped white chocolate in a circle but leave the middle empty. Using a pizza cutter cut the dough into 12 wedges. Starting at curved edge, roll up each wedge and place point-side down, on an ungreased baking sheet. Repeat with the remaining dough.
In a small bowl stir together the sugar and cinnamon if desired and sprinkle over each cookie. If you are trying to cut back on sugar, you can skip this step.
Bake at 375° F / 190° C for 20 to 25 min or until light golden brown.
Recipe by Baking Glory at http://www.bakingglory.com/recipes/cookies/apricot-rugelach/