1. Preheat oven to 350°F/180°C. Grease a 9×9 inch (23×23 cm) square cake pan; set aside. In a medium bowl, melt semi-sweet chocolate chips and butter using microwave, stirring every 15 seconds. Stir in milk. Let stand 2 minutes. Beat in eggs and vanilla until smooth; set aside.
2. In another bowl, sift together sugar, flour and cocoa powder. Pour chocolate mixture over dry ingredients and stir together. Measure out 1/4 cup of the batter; set aside. Spread remaining batter into prepared pan.
1. In a medium bowl, melt peanut butter chips using microwave, stirring every 15 seconds; set aside. In another medium bowl, beat together cream cheese, sugar, flour, egg and milk. Pour in melted peanut butter chips and beat until smooth.
2. To assemble spoon cheesecake batter over the brownie batter; spread evenly. Drop spoonfuls of the remaining brownie batter over top and swirl with a knife to create a marble effect. Bake for 35-40 minutes or until set. Cool completely before cutting.
Recipe provided by Dairy Farmers of Canada. For more recipe ideas visit dairygoodness.ca