Melt chocolate and butter in a medium saucepan set over a pan of simmering water over medium-low heat, stirring occasionally until smooth.
Meanwhile, soften gelatin in 1 tbsp. warm water in a small bowl, and set aside.
Separate eggs, putting yolks into a small bowl and whites into a large mixing bowl. Beat egg whites with an electric mixer on medium speed until they form medium-stiff peaks, about 3 minutes. Fold softened gelatin into whites, using a rubber spatula, and set aside.
Remove saucepan from heat, and beat in egg yolks with a wooden spoon, then return pan to heat for 2 minutes, stirring chocolate mixture constantly. Remove pan from heat. Add about a third of the egg whites to the chocolate, and gently fold whites and chocolate together with a rubber spatula. Repeat, carefully folding in remaining egg whites.
Spoon pudding into small dessert cups, cover with plastic wrap, and refrigerate for at least 2 hours or overnight. Serve in bed with some whipped cream, if you like.