Step by step

1. Put the chocolate and butter in a bowl and let it melt in the microwave for 30 seconds. Let cool slightly.

2. Separate the eggs. Add the egg yolks to the chocolate mixture and mix it well.

3. Put the egg whites into the stand mixer bowl. Attach the Wire Whip and whip on speed 10 until soft peaks form. Gradually add sugar and whip until stiff peaks form.

4. Fold the chocolate mixture gently under the egg whites. Pour in a lightly greased 24 cm cake tin.

5. Bake for 50 minutes in a 135°C oven. Let cool in opened oven. Unmold the tin when completely cooled down.