Drain 2 (16 oz.) cartons non-fat yogurt overnight. Add:

8 tbsp. sugar
3 tbsp. cornstarch
1/4 c. unsweetened cocoa
3 egg whites or 1/2 c. egg substitute
1/2 c. powdered skim milk

Optional: 1 teaspoon mint or almond extract

Mix all ingredients with a wire whisk until blended. Pour into an 8" round baking dish. (Spray with non-stick spray.) Bake 50 to 60 minutes at 325 degrees. Chill 2 hours or overnight before serving.