place a medium sauce pan with water in the stove

inside of the medium pan place a smaller one with the chocolate and the butter

stir until melts

add the yolks one by one and stir continually

add the sugar stir well and take from the heat

beat the whites until fluffy and double in volume

add the withes to the chocolate mixture and mix slowly and carefully (to not lose the nice volume )

take to fridge 4hours before serve