1. Heat oven to 350°F. Grease 13x9x2-inch baking pan.
2. Beat butter and peanut butter in large bowl. Add granulated sugar and brown sugar; beat well. Add eggs, one at a time, beating well after each addition. Blend in vanilla.
3. Stir together flour, baking powder and salt; mix into peanut butter mixture, blending well. Stir in peanut butter chips. Spread half of batter in prepared pan; spoon syrup over top. Carefully top with remaining batter; swirl with metal spatula or knife for marbled effect.
4. Bake 35 to 40 minutes or until lightly browned. Cool completely in pan on wire rack. Cut into squares. Makes 24 to 36 brownies.