Homemade Chocolate Pop Tarts from Little Acorn (makes 8 large pastries)
1 box frozen, pre-rolled all-butter puff pastry
1-1.5 bars dark chocolate, cut into 8 equal-size pieces
1 egg mixed with a tablespoon of water
Lay one sheet of cold but thawed puff pastry on the counter with the long sides at the top and bottom. Evenly space the 8 pieces of chocolate on top of the dough—four rows on the top half of the pastry, and four rows on the bottom (Little Acorn has a helpful diagram if you find these directions confusing.)
Use a pastry brush to paint egg wash around the chocolate. Lay the top sheet of pastry over the chocolate. Push down between the chocolate and on the outside edges. Use a pizza wheel or knife to cut between the chocolate to make individual pastries. Crimp the edges using a fork. Brush egg wash onto the tops of your pastries
Put on a parchment-lined sheet pan and freeze until hard. Then wrap each uncooked pastry tightly, and store in the freezer until ready to bake.
To bake: Preheat oven to 400F. Place completely frozen pastries on a parchment-lined sheet pan. Bake for 20 minutes, until puffed and darkly golden. Dust with icing sugar.