WAFER Mixture: Line 8-inch pan with 9 of the wafers. Place butter and brown sugar in large saucepan. Add milk and vanilla; stir. Bring to boil on medium-high heat; cook 5 min. Remove from heat.

ADD graham crumbs and peanut butter; mix well. Pour over wafers in pan; cover with remaining 9 wafers. Refrigerate 1 hour or until firm.

ICING:
BEAT butter and peanut butter in large bowl until well blended. Add icing sugar, milk and vanilla; mix well. Spread over chilled wafer mixture in pan. Cut into 36 squares to serve. Store leftovers in refrigerator.