Melt 3 tablespoon butter and 1 square (1 ounce) unsweetened chocolate in a saucepan. Mix 1/4 cup unsweetened cocoa with 3/4 cup sugar, and blend in; dloely d yit in 1/2 cup light cream or, evaporated milk. Bring to boil, stirring well with a wire whip for 10 seconds.       Remove from heat, and blend in 1/8 teaspoon salt and 1 teaspoon vanilla.

Source: Julia Child