For Crust: Place margarine in the microwave pan. Cook, uncovered, on HIGH for 45-60 seconds or until melted. Stir in crushed chocolate wafers until all is moistened. Press mixture firmly against bottom and sides of pan. Cook, uncovered, on HIGH for 11 1/2 minutes or until set, rotating pan a half-turn after 30 seconds.

For Filling: In medium mixing bowl combine cream cheese, sour cream, sugar, milk, and egg; beat with an electric mixer on medium speed just until smooth. Stir in 2 oz. melted chocolate and vanilla. Pour cream cheese mixture into crust. Cook, uncovered, on MEDIUM for 11-14 minutes or until a knife inserted 2 inches from edge comes out clean, giving dish a quarter-turn every 3 minutes. (Center will be slightly set, but not firm.) Cool slightly, then refrigerate at least 4 hours or until set.

For Topping: (optional) In a 1 3/4 quart casserole cook remaining 1 oz. chocolate and shortening, uncovered, on HIGH for 2-3 minutes or until melted; stir until smooth. Drizzle chocolate mixture on top of cheesecake.

Per serving: 405 cal, 30 g fat, 86 mg chol