Fudgy Cheesecake Swirl Brownies

Melt butter and baking bars in a medium, heavy-duty saucepan over low heat, stirring until smooth. Cool to room temperature. Stir in 1 3/4 cups sugar. Beat in 3 eggs; stir in flour. Spread into greased 13 x 9-inch baking pan. Beat cream cheese and remaining 1/2 cup sugar in small mixer bowl. Beat in remaining egg and vanilla extract. Pour over chocolate mixture; deeply swirl batters with knife. Bake in preheated 350ºF (175ºC) oven for 30 to 35 minutes or until wooden pick inserted near center comes out slightly sticky. Cool completely in pan on wire rack.