Mix graham cracker crumbs, butter, confectioners' sugar, and 1 cup peanut butter in a bowl until well blended; press evenly into the bottom of an ungreased 9x13-inch pan.
Melt 3/4 cup dark chocolate, milk chocolate, and 1/4 cup peanut butter in the top of a double boiler over simmering water; heat, stirring occasionally, until smooth, 5 to 10 minutes. Spread chocolate-peanut butter mixture over graham cracker layer in 9x13-inch pan.
Melt 1 cup dark chocolate and milk in the top of a double boiler over simmering water, stirring until smooth, 3 to 5 minutes; pour over chocolate-peanut butter layer. Refrigerate until set, at least 1 hour. Cut into squares to serve.