How to cook
Beat the butter with the sugar and egg. Stirring continuously, add the yoghurt, liqueur and grated orange zest. Separately, mix the flour with the cocoa. Carefully add this to the wet mixture and stir gently.
Crumble the chocolate into small pieces and add it to the dough. Stir the mixture and distribute it out into oiled muffin forms.
Bake the muffins in a preheated 390°F (200 °C) oven for about 20 minutes.