Preheat oven to 350*. Mix brownies according to package. Spread in greased 9x13 pan.
Beat cream cheese, butter and cornstarch until fluffy. Beat in milk, egg, and vanilla until smooth. Stir in your chopped candy bars.
Spoon cheesecake batter on top of the brownie batter. Bake 40-45 minutes. Cool on wire rack.
Cut into bars and drizzle with peanut butter and chocolate candy melts and sprinkle Reese's pieces on top of that. Refrigerate. Cut into 24 squares.