Preheat the oven to 220° for 15 minutes.
Melt your chocolate and butter (in the microwave or bain-marie).
Then add your sugar and eggs.
Beat with a whisk, then pour in your flour.
Then pour the preparation into small silicone molds (or if you don't have any, you can possibly try the adventure of the giant muffin in a normal cake dish:which works very well too).
Then cook for 10 minutes, and a little more if necessary.
To unmold, wait for the muffins to cool.
To be enjoyed with custard or a scoop of vanilla ice cream!