Pain au Chocolate

Stir together yeast and ½ cup water heated to 115 F (46 C) together in the bowl of a stand mixer fitted with a dough hook; let sit until foamy, about 10 minutes.

Stir in milk, sugar, 3 tbsp. melted butter, powdered milk, and salt; add flour. Mix on medium speed until a stiff dough forms, about 5 minutes. Transfer to a work surface and form into a thick square; wrap in plastic wrap and refrigerate for 2 hours.

Place remaining butter on a sheet of plastic wrap; cover with another sheet. Using a rolling pin, pound and shape butter into a 6″, ½″-thick square; set aside. Using rolling pin, roll dough into an 16″ square on a lightly floured work surface.

Unwrap butter square, and place on dough so its corners line up with the middle point of each side of dough square; fold dough corners over butter so they meet in the center. Roll dough into a 12″ x 9″ rectangle, and then tri-fold dough like a letter.

Roll the dough into a 12″ x 9″ rectangle and repeat folding. Wrap in plastic wrap; chill for 30 minutes. Repeat rolling and folding dough twice more; chill for 1 hour.

Roll dough into a 20″ x 14″ x ¼″ thick sheet; halve lengthwise. Cut each half into about 9 triangles, about 3 ½″-wide at their base; cut a ½″-deep slit in the middle of each wide base.

Cut chocolate into bars (strips) that are roughly 1/2" by 3 1/2" long. The length of your strip should span the entire width of a 4 oz baking bar. You should be able to get 16 strips from a 4 oz bar. Place 1 chocolate strip parallel to the base near the cut; holding the tip of the opposite corner down, roll the base over the chocolate toward the tip until it forms a tight roll.

Place croissant on a parchment paper-lined baking sheet, tip side down, and brush with egg wash. Repeat with remaining triangles, bars, and egg wash. Let croissants sit until doubled in size, about 2 ½–3 hours.

Heat oven to 375 F (190 C). Working with one baking sheet at a time, brush croissants with more egg wash; bake until deep golden brown, about 20 minutes.