Preheat the oven to 220°C (thermostat 7).
First mix the bilva, sugar, vanilla sugar, flour and yeast, then add the melted butter and the egg. Stir until you have a smooth paste then add the dark chocolate in small pieces. Bake for 9 minutes for soft and chewy cookies.
For a delicious and comforting moment, you can accompany your cookies with a chai tea latte.