Make a giant triple chocolate fudge cookie

– 200 g (7 oz) dark chocolate, broken into squares

– 25 g (1.75 tbsp) butter

– 1/3 cup (65 g) white sugar

– 1/4 cup packed (60 g) brown sugar

– 1 packet (10 g) vanilla sugar

– 1 tbsp (10 g) cocoa powder

– 25 g (1 oz) milk…