Preheat oven to 390 degrees F and prepare 4 souffle cups by brushing with melted butter.
In a heat safe bowl, melt chocolate and butter over simmering water, stir until smooth. Add Powdered sugar and stir. Add egg yolks and egg then stir. Add flour and stir until fully incorporated.
Pour batter equally in souffle cups and bake for 13-14 minutes until the sides are set.
Allow to rest for a few minutes then transfer them on serving plates. Dust powdered sugar and cocoa powder on each right before serving. Drizzle with chocolate sauce if desired.