Using bain marie method, melt chocolate and butter together in a mixing bowl.
In a mixing bowl, whisk the eggs, until slightly foamy.
Add your sugar into the egg mixture and continue to whisk/whip the eggs until a white, pale foam without anymore yellow liquid at the bottom.
Add your melted chocolate & butter mix in half batches - continue to whisk until you get a thick custardy mixture.
Using a silicon spatula and a sieve, sieve in your flour in half batches. Slowly fold in the the flour until you get a consistent mix.
Pour your mixture into the your moulds and chill them for roughly 20 minutes before baking them off at 190 deg C for about 15mins.