Preheat the oven to 210 ° C top / bottom heat. Brush 2 porcelain dishes with soft butter.
Melt the chocolate and butter together in the microwave or on a double boiler. Mix in the eggs and sugar with the whisk, stir in cocoa powder and flour, then stir in the butter and chocolate mixture.
Pour the mixture into the tins up to 0.5 cm below the rim and bake in the preheated oven on the middle rack for 11 minutes.