BEAT sugar, peanut butter and butter in large bowl with electric mixer on medium speed until well blended. Beat in eggs and vanilla. Mix in flour and salt. Stir in chocolate.
SPREAD batter in greased foil-lined 9-inch square baking pan. Drop jam by spoonfuls over batter; swirl with knife to marbelize.
BAKE at 350°F for 35 to 40 minutes or until toothpick inserted in center comes out almost clean. DO NOT OVERBAKE. Cool in pan. Cut into squares.
Storage Know-How: Store, tightly wrapped in foil, for up to 5 days.