Melt the chocolate with butter in a bain-marie and separately beat the eggs with sugar (always in bain-marie). Out of the heat add the chocolate and butter, then the flour. Fill the bottom of 11 silicone muffin moulds with the mixture and put a piece of dark chocolate in the center, then cover with the remaining mixture up to 3/4 of the mould.
Bake in the preheated oven at 175°C for 12-13 minutes (the time depends a lot on the oven). Serve hot with a sprinkling of powdered sugar on top and with a spoonful of mango cream obtained by blending a fresh mango.