Pour the water into a bread machine pan; add the flour. Sprinkle the milk powder over the flour. Place the sugar, salt, and 2 tablespoons of softened butter into the corners of the pan. Make a small indent in the top of the dry ingredients and put the yeast in the indent. Run the bread machine on the basic dough setting.
Meanwhile, lay out a sheet of waxed or parchment paper. Shape the remaining 1/2 cup of butter into a 8x13cm rectangle on the waxed paper; wrap and chill until ready to use.
Remove the butter from the refrigerator and allow to soften while you roll out the dough. Turn the dough out onto a lightly floured surface. Roll the dough into a 20x30cm rectangle. Place the butter on half of the dough, leaving a 1.5cm border of dough on 3 sides. Fold the other half of the dough over the butter and press the edges firmly to seal.
Roll the dough out to a 16x36cm rectangle. Fold the dough in thirds from the long ends, as you would fold a business letter. Cover the dough loosely with plastic wrap and refrigerate for 20 minutes.
Remove the dough from the refrigerator. Place it onto a lightly floured surface so that the folded edge faces you. Roll the dough out again into a 16x36cm rectangle, and fold into thirds. Cover with plastic and chill for 20 minutes.
Repeat step 5, chilling for 30 minutes.
In a small bowl, beat together the egg yolk and milk; set aside. Grease two baking trays.
Roll the dough out into a 31x55cm rectangle. Cut the dough into thirds in both directions, to make 9 rectangles. Divide the chocolate among the rectangles. Lightly brush the egg yolk mixture around the edges of each piece. Starting at a short end, roll each piece of dough around the chocolate as if you were rolling a cigar. Press the edges together to seal.
Place the pastries onto the prepared baking trays; cover with greased plastic wrap and allow to rise in a warm place until they have doubled in size, about 30 minutes.
Preheat oven to 200 degrees C (400 degrees F).
Brush the top of the pastries with the remaining egg yolk mixture.
Bake in the preheated oven until golden brown, about 15 minutes. Cool for 5 minutes on the baking tray, then transfer pastries to wire racks. Serve warm or at room temperature.