Line tray or cookie sheet with waxed paper. In 2-qt glass measuring cup with handle, combine chips and shortening. Microwave in High for 1 1/2 to 2 minutes until chips are melted and mixture is smooth when stirred. With fork, dip each cookie into chip misture; gently tap fork on side of cup to remove excess chocolate. Place coated cookies on prepared tray; top each cookie with a graham snack cracker. Chill until chocolate is set, about 30 minutes. Store in airtight container in cool, dry place. Makes about 4 dozen.