Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper and set aside. Break or chop your chocolate into tabs and set aside.
Pre-rolled puff pastry, that you get at the store, is usually rolled out very thinly, so we are doing a double pastry for this recipe, to mimic a bit of a thicker dough for pain au chocolat. -->Place one sheet of pastry on your working surface (lined with parchment), brush it with melted butter, then place another sheet of puff pastry directly over it. Trim the sides if there’s any weird overlap, to create a nice, sharp rectangle (the exact measurements will depend on the brand of puff pastry you bought, as every company seems to have its own size).
Cut your rectangle vertically into thin strips, so you get smaller rectangles, about 2,5 x 9 inches (6 x 23 cm) large. Place a few pieces of chocolate on one end of each strip (to create a log that spreads from side to side) and roll the dough up, just to cover the chocolate. Add another log of chocolate and finish rolling the dough all the way up. The chocolate will be hidden in the center. Repeat with remaining dough and place croissants on the baking sheet, seam side down.
Whisk egg in a small bowl with 1 tablespoon of water. Lightly brush each croissant with the egg wash and sprinkle with flaked almonds (optional). Bake croissants in the middle of the oven for 15-20 minutes, until they are puffy and golden brown on top.
Remove from oven, allow to cool for a few minutes before serving. Dust with powdered sugar right before serving (if you want, this is totally optional).Store leftover croissants covered at room temperature or in the freezer for 2-3 months, although keep in mind that these taste best fresh.
Notes
About the pastry:
the pastry used in this recipe is the basic puff pastry, that is made without yeast. However most, if not all of the recipes I’ve checked use homemade yeasted puff pastry for pain au chocolat. You CAN buy yeasted puff pastry, if the name on the packaged doesn’t suggest that, check the ingredients list.
Because this type of pastry has yeast in it, you need to let your croissants rest at room temperature, to activate that yeast. So once your croissants are rolled, loosely cover them and let them rest at room temperature for about 45-60 minutes. Then do the egg wash and bake them for 15-20 minutes.
Traditionally, chocolate croissants are made with chocolate batons. If you want a uniform look, you can get these on Amazon or at specialty stores. If using chocolate batons, cut the dough into strips that match the length of these batons. You don’t chocolate to stick out of the pastry. This video greatly demonstrates what I’m talking about.