1. For yogurt cheese: Line a yogurt strainer, sieve, or a small colander with three layers of 100-percent-cotton cheesecloth or a clean paper coffee filter. Suspend lined strainer, sieve, or colander over a large bowl. Spoon yogurt into the strainer, sieve, or colander. Cover with plastic wrap. Refrigerate for 24 hours. Remove from refrigerator. Discard liquid. Set yogurt cheese aside.
2. In a small saucepan, sprinkle 2 1/2 teaspoons of the gelatin over the milk; let stand for 5 minutes. Bruise mint sprigs by pressing with the back of a spoon; add to saucepan. Heat and stir milk mixture over low heat just until gelatin is dissolved. Remove from heat. Cool for 15 minutes. Remove and discard mint sprigs; set aside.
3. Place the 1 cup raspberries in a food processor or blender. Cover and process or blend until smooth. Transfer raspberry puree to another small saucepan. Stir in the 3 tablespoons sugar. Sprinkle remaining 1-1/4 teaspoons gelatin over raspberry mixture; let stand for 5 minutes. Heat and stir raspberry mixture over low heat just until gelatin is dissolved. Remove from heat; cover and chill for 15 minutes.
4. In a large bowl, beat cream cheese with an electric mixer on medium speed until smooth. Beat in yogurt cheese, the 1/3 cup sugar, and the vanilla until smooth. Gradually beat in milk mixture. Add 1/2 cup of the cream cheese mixture to the raspberry mixture; stir until well mixed. Set aside.
5. Spoon half of the the white cream cheese mixture into a 7- to 8-inch springform pan. Spoon half of the raspberry mixture into mounds over white cream cheese mixture. Using a narrow, thin-bladed metal spatula or a table knife, swirl raspberry mixture into white mixture. Repeat layering remaining white cream cheese mixture and raspberry mixture. Cover and chill for 24 hours.
6. To serve, using a small sharp knife, loosen cheesecake from side of springform pan; remove side of pan. Cut cheesecake into wedges. Drizzle Raspberry Sauce on twelve dessert plates. Place cheesecake wedges atop sauce on plates. If desired, garnish with fresh raspberries and fresh mint leaves. Makes 12 (1 slice and 1 1/2 tablespoons) servings.
Raspberry Sauce: Place 2 cups fresh raspberries in a blender or food processor. Cover and blend or process until smooth. Press mixture through a fine mesh sieve; discard seeds.
*Test Kitchen Tip: Be sure to use a brand of yogurt that contains no gums, gelatin, or fillers. These ingredients may prevent the whey from separating from the curd to make yogurt cheese.
**Sugar Substitutes: Choose from Equal® Spoonful or packets or Sweet 'N Low® bulk or packets. Follow package directions to use product amount equivalent to 3 tablespoons and 1/3 cup sugar.
PER SERVING WITH SUBSTITUTE: same as above, except 137 cal., 12 g carbo. Exchanges: 0.5 other carbo.