Melt the chocolate with the butterPreheat the oven to 180°C. In the microwave, melt the chocolate with the butter. Mix and let it cool down.
2Prepare the batter and bakeIn a bowl, beat the egg whites until stiff, then add the sugar, flour and melted chocolate. Whisk for 1 minute. Pour the mixture halfway into a buttered and floured mold approximately 15 cm in diameter. Bake for 15 minutes.