Melt the butter and mix with the sugar. Let cool down.
Mix the flour, baking powder and salt in a large bowl.
Stir in butter mixture and yoghurt. Fold in chocolate chunks. Stay in the fridge for 3 hours! or rest overnight. Heat the oven to 180 degrees. Form balls with a tablespoon or cookie spoon, if the dough is too hard, wait 20 minutes and place the dough balls with space on a baking sheet. Bake in the hot oven for 9-12 minutes. Allow to cool briefly on the plate and then place on a grid and allow to cool completely.