1. Preheat oven to 400 degree F and lightly grease a large cookie sheet.
2. Whisk together granulated sugar and cinnamon. Stir together raisins and walnuts in another small bowl.
3. Unfold 1 pastry sheet and roll out on a lightly floured surface into a 16x10-inch rectangle. Brush top of pastry lightly with water and sprinkle with half of cinnamon sugar, then half of raisin-walnut mixture, leaving a 1/2-inch border on all sides. Beginning with a long side, roll up pastry (not too tightly) to encase filling completely. Join ends of roll together, pressing them to form a single ring, and carefully transfer to one half of prepared cookie sheet, seam side down. Brush top of roll with beaten egg, especially where ends are joined, but do not allow egg to drip down onto cookie sheet. Keep pastry ring chilled while repeating process with remaining pastry, filling and egg wash. Cut rings with a serrated knife, making about 7 (1-1/2-inch) diagonal cuts in each ring, but keeping it intact and fanning out cut pieces slightly (this will help inside of pastry cook evenly). Freeze rings on cookie sheet until really firm, about 10 minutes. Bake rings in middle of oven until golden brown on top and cooked through inside, about 30 minutes. Carefully transfer with large metal spatulas to a rack to cool.
4. Whisk together confectioners' sugar and cream until smooth. Pipe or drizzle icing over rings in a zigzag pattern.