Butter or spray 6 ramekins or 1 (6-inch) cake pan.
In a double boiler melt chocolate, liquid, and butter. Beat egg yolks until light and fluffy. Add melted chocolate mixture. In bowl of mixer beat egg whites and sugar to stiff peak stage. Fold chocolate mixture into meringue. Pour into ramekins or cake pan and bake in oven for about 20 minutes. Remove from oven and serve immediately.