1. Heat oven to 350°F. Grease 13x9x2-inch baking pan.
2. Prepare peanut butter filling by beating cream cheese, peanut butter, 1/4 cup sugar, 1 egg and milk.
3. Melt butter in large microwave-safe bowl at HIGH (100%) 2 to 2-1/2 minutes or until melted. Stir in remaining 2 cups sugar and vanilla. Add remaining 3 eggs, one at a time, beating well with spoon after each addition. Add cocoa; beat until well blended. Add flour, baking powder and salt; beat well. Stir in chocolate chips.
4. Remove 1 cup batter; set aside. Pour remaining batter into prepared pan. Spread peanut butter filling over surface. Drop reserved chocolate batter by teaspoons over filling. Using knife, gently swirl through top layers for marbled effect.
5. Bake 35 to 40 minutes or until wooden pick inserted in center comes out almost clean. Cool completely in pan on wire rack. Cut into bars. Makes about 24 brownies.