Mix the butter with sugar, add the egg and mix in. Mix flour with baking powder and add in portions. Alternatively, stir everything together in a food processor with a rubber lip mixer. Fold in the chopped cashew nuts and chocolate. Shape the dough into small balls with 2 teaspoons or an ice cream scoop and place on a baking sheet lined with baking paper. Press gently with wet fingers.
Bake in the hot oven for about 10-15 minutes. Let cool down completely.