My Tante Ursel shared this with me many years ago. It's super simple and the best I've had. Make sure to use good quality chocolate!
2 bars bittersweet chocolate (100 g ea)
3 eggs, separated
2 Tablespoons sugar
2 cups heavy cream
Melt chocolate in microwave and cool slightly. Cream the egg yolks with 2 T hot water and the sugar. Mix in the melted chocolate. Whip the cream until stiff then add to chocolate mixture. Whip the egg whites until stiff, fold into chocolate mixture. Refrigerate until cold.