In the bowl of a food processor or using a pastry cutter, cut the butter into the flour, pulsing until you have large crumbs. Add the egg yolk and creme fraiche and continue to pulse (or knead by hand) until the dough comes together in a ball. Wrap the dough in plastic wrap and chill in the refrigerator for 2-3 hours.
Make the filling by tossing together the cranberries, sugar, pecans, almonds and cinnamon in a small bowl.
Preheat the oven to 350° F.
Divide the dough into three equal parts and form into balls. On a floured surface, roll out 1 ball of dough into a circle about 1/8 inch thick. Sprinkle with the filling, then cut into 12 equal wedges. Starting at the outside edge, roll each wedge from the widest to the smallest point, creating a crescent shape. Repeat with the other two pieces of dough.
Place the cookies on a parchment lined baking tray. Chill in the refrigerator for about 10 minutes. Right before baking, lightly brush with the egg white. Bake for about 18-20 minutes, or until the cookies are golden.
Recipe lightly adapted from my friend Linda's Butterhorns.