Melt the chocolate with the butter in a water bath. Beat the whole eggs and the egg whites with the sugar until fluffy in texture. While continuously beating with a mixer, pour the chocolate mixture in to the egg mixture and beat well.
Brush cupcakes lightly with butter at room temperature and fill them up just past the middle. Put them for 2 hours in the refrigerator.
Preheat the oven and place the cupcakes to bake for about 8 minutes - enough to inflate slightly and catch a crust, but their core must remain liquid. Serve the petit gateau chocolate lava cakes inverted on a plate and top them with a scoop of vanilla ice cream.