Mix vanilla wafer crumbs, margarine, and 1 teaspoon Equal for Recipes in bottom of 9-inch springform pan. Reserve 1 tablespoon crumb mixture. Pat remaining evenly on bottom and 1/2-inch up side of pan. Bake in preheated 350 degree oven until crust is lightly browned, about 8 minutes. Cool on wire rack.

Beat cream cheese and 5 1/2 teaspoons Equal for Recipes in large bowl until fluffy; beat in eggs, egg whites, and cornstarch. Mix in sour cream and vanilla until well blended. Remove 1/2 cup of cheesecake mixture. Pour remaining mixture into crust in pan.

Add melted semi-sweet chocolate to 1/2 cup reserved cheesecake batter. Mix thoroughly. Place dollops of chocolate mixture on top of cheesecake. Using a butter knife or spatula, gently swirl chocolate mixture into cheesecake.

Place cheesecake in roasting pan on oven rack; add 1-inch hot water to roasting pan. Bake in preheated 300 degree oven just until set in center, 45 to 60 minutes. Remove cheesecake from roasting pan, sprinkle with reserved crumbs and return to oven. Turn oven off and let cheesecake cool in oven with door ajar for 3 hours. Refrigerate 8 hours or overnight.

Remove side of pan; place cheesecake on serving plate.

This recipe yields 16 servings. Serving size: 1 slice.

Exchanges Per Serving: 2 1/2 Fat, 1 Milk.

Nutrition Facts: Calories 206; Total Fat 13g; Cholesterol 55mg; Sodium 243mg; Carbohydrate 15g; Protein 8g.