Preheat oven to 350°. Grease a 10 by 3-inch springform pan.
In a 3-quart saucepan over low heat, heat chocolate, butter or margarine, sugar, half-and-half, vanilla extract and salt until chocolate melts and mixture is smooth, stirring constantly.
In a large bowl, beat eggs slightly. Beat chocolate mixture into eggs.
Pour into prepared springform pan. Bake in the preheated oven for 45 minutes or until a toothpick inserted 2 inches from the edge comes out clean.
Cool cake completely on a wire rack. When cake is cool, remove side of pan. Wrap cake in plastic wrap and refrigerate until well chilled, at least 6 hours.
When cake is completely chilled, prepare Chocolate Frosting. Spread over top and sides of cake. Prepare whipped cream until stiff peaks form. Pipe around edge of cake, if desired, or serve with each slice. Refrigerate cake if not serving immediately.
Combine all ingredients and beat until smooth, adding more half-and-half if necessary to reach spreading consistency.