Cream butter, sugar, eggs and vanilla in large mixer bowl until light and fluffy. Combine flour, cocoa, and baking soda; add alternately with syrup to creamed mixture. Stir in peanut butter chips. Spread in greased 13 x 9 inch pan. Bake at 350 degrees for 30 to 35 minutes or until brownie begins to pull away from edges of pan. Cool; frost if desired. Cut into squares.
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