Place peanut butter in TupperWave® Stack Cooker 1¾-Qt./1.75 L Casserole and microwave on high power 1 minute. Stir powdered sugar and 1 cup crushed pretzels into peanut butter. Add mixture to UltraPro 2-Qt./2 L Casserole Pan and press down until even.
Add chocolate, Set & Serve
Microwave chocolate chips in 30 second intervals, stirring in between, until melted. Drizzle chocolate over peanut butter mixture and add additional pretzels for topping, if desired. Refrigerate until chocolate is set, about 10 minutes. Cut into squares using spatula and store in sealed Tupperware container until ready to eat.