Line a 9 x 9-inch pan or baking dish with heavy duty aluminum foil leaving a 2-inch overhang to create handles to remove the bars from the pan. Spray lightly with cooking spray.
In a large mixing bowl, use a mixer to beat together 1 1/4 cup peanut butter, 1 cup powdered sugar, 1 1/2 sticks softened butter and vanilla until smooth.
By hand mix in 3 cup chopped pretzels, 1 cup powdered sugar and 1/2 cup chocolate chips. Stir until fully moistened. Press the peanut butter pretzel mixture firmly and evenly into the pan.
In a small microwave-safe bowl, melt the remaining chocolate chips and 3/4 cup peanut butter in 30-second intervals. Repeat stirring until completely smooth. Pour over the pretzel bars and spread evenly.
Sprinkle the top with the remaining 1/2 cup broken pretzels and chopped peanuts. Refrigerate for at least 4 hours to set. You can freeze to speed up the process.
Use foil handles to lift the bars from the pan. Use a sharp knife to cut into squares and serve. Store chilled for up to 5 days.
Notes
Double Batch: These bars could be made in a 13x9-inch pan only if you double the recipe or they will be very thin.
Peanut Butter: You could adapt this recipe using other nut butters such as almond butter. You could also use chunky peanut butter or natural peanut butter.Â
Chocolate: You can use milk chocolate chips, dark chocolate chips or a combination of chocolate chips for the chocolate topping.
Pretzels: To crush the pretzels, place them in a plastic bag and gently pound them with a rolling pin. Alternatively, you can chop them on a cutting board with a knife or pulse them a few times in a food processor. Aim for coarse crumbs—avoid grinding them too fine.
Chill Thoroughly: It's very important to give these bars time to set-up before you attempt to cut them. Allow ample time to chill them thoroughly and also store any leftovers chilled. I found that the bars hold together better and they'll cut into prettier pieces as well.