Grease the molds with butter. Preheat the oven to 180 ° C. Melt the butter and chocolate in the saucepan over a low heat.
Beat eggs and sugar until frothy. Stir in the chocolate mixture. Add the flour and stir in. Sprinkle the molds with cocoa powder and add the batter. Bake the muffins for 10-12 minutes.
After approx. 8 minutes do the chopsticks test. The muffins should be crispy on the outside and soft on the inside.