1. Heat oven to 350°F. Grease 9-inch springform pan. Set aside 1 tablespoon each milk chocolate chips and peanut butter chips for drizzle.
2. Stir together butter, sugar and vanilla in large bowl with spoon or wire whisk. Add eggs; stir until well blended. Stir in flour, cocoa, baking powder and salt; blend well. Spread in prepared pan.
3. Bake 25 to 30 minutes or until brownie begins to pull away from side of pan. Meanwhile make cheesecake layer.
4. Immediately after removing brownie from oven, sprinkle remaining milk chocolate chips and peanut butter chips over brownie surface. Spoon cheesecake mixture over chips. Return to oven; continue baking 45 to 50 minutes or until almost set. Remove from oven to wire rack. With knife, loosen cake from side of pan. Cool 2 hours; cover. Refrigerate 3 to 4 hours or until thoroughly chilled. Remove side of pan.
5. Stir together reserved milk chocolate chips, reserved peanut butter chips and 1/2 teaspoon shortening in small microwave-safe bowl. Microwave at MEDIUM (50%) 30 seconds; stir. If necessary, microwave at MEDIUM 10 seconds at a time, stirring after heating, until chips are melted and mixture is smooth when stirred. Drizzle over top of cheesecake. Store, covered, in refrigerator. 10 to 12 servings.
CHEESECAKE LAYER: Beat 3 packages (8 oz. each) softened cream cheese and 3/4 cup sugar until smooth in large mixer bowl. Add 3 eggs, one at a time, beating well after each addition. Stir in 1 teaspoon vanilla extract.