In a large bowl, combine the graham cracker crumbs, butter, confectioners' sugar, and peanut butter. Mix until well combined., Spread the mixture in a lightly greased 9" x 13" pan. Chill in the refrigerator for approximately 10 minutes., While the peanut butter layer is chilling, melt the chocolate chips, in a microwave oven or in a double boiler on top of the stove. Spread the chocolate over the peanut butter., Cut the bars into squares, or use a 1 1/2" to 2" heart cookie cutter to cut them into hearts. Leave them in the pan. Return them to the refrigerator to chill for at least 1 hour., Store well wrapped at cool room temperature for several days; freeze for longer storage.