puff pastry squares
1 egg + 1 tbsp water, beaten
Preheat oven to 400 degrees. Place 2 squares of chocolate and half a large marshmallow (or a few mini marshmallows) at the center of each puff pastry square. Fold in half to form a triangle and press down to close all around. Brush with eggwash and sprinkle with demerara sugar. Bake until puffed and golden.