In a microwave, microwave the chocolate, 1/4 cup water and butter until the chocolate and butter are melted; stir until smooth. Cool for 10 minutes.
In a small heavy saucepan, whisk egg yolks, sugar and remaining water. Cook and stir over medium heat until mixture reaches 160° or is thick enough to coat the back of a metal spoon. Remove from the heat; whisk in chocolate mixture.
Set saucepan in ice and stir until cooled, 5-10 minutes. Fold in whipped cream. Spoon into dessert dishes. Refrigerate 4 hours or overnight.