Thaw sheet at room temperature 30 minutes.
Preheat oven to 400 degrees.
Mix chocolate pieces and walnuts and set aside.
Unfold pastry on lightly floured surface.
Roll into a 12 inch square and cut into 9 squares.
Place about 2 tablespoons chocolate mixture in center of each square.
Brush edges of squares with water.
Fold corners to center on top of filling and twist tightly to seal.
Fan out corners.
Place 2 inches apart on baking sheet.
Bake 15 minutes or until golden.
Remove from baking sheet and cool on wire rack 10 minutes.
Sprinkle with powdered sugar.
If desired, garnish with fresh raspberries, chocolate curls and fresh mint.