Gather the ingredients.

Pour water into a bread machine pan; add flour, milk powder, sugar, salt, and 2 tablespoons of softened butter. Add yeast and run on basic dough setting.

Shape ½ cup butter into a 3x5-inch rectangle and chill.

Roll dough to a 8x12-inch rectangle. Place butter on half, fold and seal edges.

Roll dough to a 6x14-inch rectangle, fold in thirds, cover with plastic wrap and refrigerate for 20 minutes.

Repeat rolling and folding process twice more with refrigeration steps of 30 minutes.

Beat egg yolk with milk. Grease two baking sheets.

Roll dough into a 12x21-inch rectangle, cut into 9 rectangles, add chocolate, brush edges with egg yolk mixture, roll dough and seal edges.

Place croissants on baking sheets, cover with greased plastic wrap, and allow to rise for 30 minutes.

Preheat oven to 400°F (200°C). Brush croissants with egg yolk mixture.