Start by pre-heating the oven to 350ºF (or 180ºC).

Melt the butter and chocolate together. Once everything has melted, stir very well and remove.

Break the eggs and separate the yolks from the whites. Add the sugar to the yolks and beat until it turns into a whitish eggnog. Now, without stopping beating, add the melted chocolate in the mixture. Beat until everything is well mixed.

Beat the egg whites until stiff and, carefully, fold the egg whites into the chocolate.

After everything is well mixed, divide the mousse in half. Store the mousse without flour in the fridge for now. To one of the halves, add the flour and mix.

Place the mousse mixture with flour in a springform pan (26 cm) greased with butter. Place in the preheated oven at 350ºF (or 180ºC) and let it bake for 12 to 15 minutes. (12 minutes it’s the ideal time for me). As soon as the cake is cooked, remove it and let it cool for about 1 hour.

After the cake has cooled, place the mousse on top. Place in the fridge for 6 to 8 hours until the mousse is very consistent.