Preheat oven to 180°C
Melt the butter and the black chocolate in a saucepan over a very low heat
In a bowl, add the flour with the sugar and the eggs, and mix well
Add the melted chocolate and butter, mix everything together and pour the paste into a buttered cake in. Let it cook in oven for 20mn
Right out of the oven, the cake seems not cooked enough: it’s normal, let cool down a few minute before remove from the pan. Now enjoy!