Stir the first 3 ingredients in a large mixing bowl; let stand until foamy, about 10 minutes. Mix the flour, sugar, cocoa and salt in another bowl. Stir 1 1/4 cups water, the egg yolk and butter into dissolved yeast; then stir in the flour mixture, 1 cup at a time, with your hands. Stir in the chocolate chips last. Knead on a lightly floured surface until velvety, elastic and moist, 8 to 10 minutes.
If done in a mixer, follow the same stages but add the chocolate chips together with the flour using the paddle. When it is blended, change to the dough hook and knead 2 minutes at low speed then 2 minutes at medium speed.
Place the dough in an oiled bowl, cover with plastic wrap and let rise about 2 hours.
Punch the dough down and cut in half. Shape into round loaves and place on an oiled baking sheet. Cover with a towel and let rise until doubled, about 1 hour.
Preheat the oven to 450 degrees F.
Bake for 15 minutes, reduce the heat to 375 degrees F and bake 30 minutes longer. Cool on a rack. Slice and enjoy for breakfast or a snack.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Louis Marchand