Move the oven racks to the upper-middle and lower-middle positions. Preheat the oven to 400°F.
Line two baking sheets with parchment paper.
PREP PUFF PASTRY AND CANDY BARS:
Remove the puff pastry sheets from the freezer and allow them to thaw for at least 15 minutes before working with them.
Unfold one sheet of puff pastry on a lightly floured surface. Cut it into 8 equal pieces.
Break the candy bars into sections. There should be four sections in each candy bar.
Place the chocolate in the center of each puff pastry piece.
MAKE EGG WASH AND ASSEMBLE PASTRY:
Make the egg wash by whisking together the egg and 1 tablespoon of water.
Fold the sides of the pastry over the chocolate and wrap the top piece over the side and press into the bottom of the packet to seal.
You can add a bit of egg wash between the pastry where you are sealing it to help hold it together.
Place the assembled pastries on the prepared baking sheets and brush the tops and sides with the egg wash.
Repeat with the second sheet of puff pastry dough.
BAKE AND COOL:
Bake the pastries for about 14-15 minutes, or until the pastry is golden brown, rotating the baking sheets halfway through baking.
Move the baking sheets to wire racks for 10 minutes.
TO FINISH:
Dust the chocolate croissant with powdered sugar and serve.
Notes
You can make these larger by cutting each puff pastry sheet into 4 equal pieces instead of 8. You will need to use bigger pieces of chocolate and increase the baking time by a few minutes.
Dark or milk chocolate will work for these. Hershey’s brand works well. I tried a couple of other brands of chocolate bar/varieties and the chocolate leaked from the pastry packet and burned.
Sealing the wrapped dough onto the underside of the pastry helps to maintain a symmetrical shape when cooking.
The egg wash will help the pastry dough stick to itself when sealing. It also gives a nice golden sheen to the baked pastry. Pastries are best served warm just out of the oven.