Disolve yeast in lukewarm milk.
Put all ingridients for the dough -exept the chocolate chunks- in a mixing bowl.
Knead to a smooth dough for minimum 5 minutes.
Cover dough and leave to rise for about 1 hour until double in size.
Put dough on a lightly floured surface and knead-in the chocolate chunks.
Divide dough in 12 equal pieces.
Form each piece to a bun.
Place buns in a baking form with baking paper.
Cover and leave to rise for about 1 hour.
Brush buns with egg yolk-milk-mixture.
Mix together, cocoa powder, flour and water for the cross.
Put in piping bag and pipe crosses on the buns.
Bake in preheated oven at 200° C for about 22 to 24 minutes.
Tastes best, warm with butter.