Water bath chocolate until creamy and set it aside.
Cut the butter into small pieces, add sugar and use a mixer to amalgamate until creamy.
Add the egg, chocolate, and flour, still mixing energetically.
Take your trustworthy whisk, put on a playlist you like - a lot -, and get ready for a bit of exercise.
Bring to a boil, whisking uninterruptedly - that's why you need good music in the background! It will take you ten to fifteen minutes, about four songs.
Stir two more minutes after boiling and remove the pot from heat.