Chocolate and walnuts are natural partners in these buttery turnovers. These delicacies are hard to resist and so easy to make - they'd be the perfect ending for your next dinner party.
Preheat oven to 400°.
In small bowl, whisk together 1 egg and 1 tablespoon water; set aside.
In large bowl, mix yogurt, 1/4 cup of the sugar, vanilla and remaining egg. Stir in flour and cocoa powder, then chocolate and walnuts.
On a lightly floured surface, roll out puff pastry sheets into 12-inch squares. With a sharp knife, cut each sheet into 9 equal squares (each 4 inches per side).
Spoon a scant 1 1/2 tablespoons chocolate-walnut filling into the center of one square. Brush edges with egg mixture; fold in half diagonally to form a triangle. Press well to seal edges; transfer to an ungreased baking sheet. Repeat with remaining pastry squares and filling.
Brush tops with egg mixture and sprinkle with remaining 1 tablespoon sugar. Bake at 400°for 14 minutes or until lightly browned on top. Cool turnovers on rack.