In food processor make graham crackers into crumbs. Add powdered sugar. In a large bowl add to butter and peanut butter. Stir well. Spoon peanut butter mixture to an ungreased 9 x 13 inch pan or for thinner layer use cookie sheet. Press firmly into an even layer with spatula. Chill about 45 minutes.
Melt chips, stirring until smooth. Spread chocolate evenly over peanut butter layer. Let stand until chocolate firms slightly. Cut into squares.