Place pretzels in a large plastic bag and crush (with a rolling pin) until well crushed (mostly crumbs and some small pretzel pieces).
In a large bowl, combine crushed pretzels, melted butter, powdered sugar and 1 cup of peanut butter.
Stir until all ingredients are well combined.
Spread mixture into a 9"x 9" casserole dish (or square cake pan) and press into an even layer.
In a small bowl, add chocolate chips and melt in the microwave (at 50% power) in 30 second intervals until mostly melted. Stir until fully melted, then add remaining 1/4 cup peanut butter and stir until smooth.
Pour, then spread chocolate topping in an even layer, then place dessert in the fridge 2-3 minutes, until the chocolate has cooled slightly, but is not firm.
Roughly chop some additional pretzels and mini peanut butter cups, remove dessert from fridge and add toppings, pressing in to the chocolate layer slightly, as needed.
Return entire dessert to the fridge and chill at least 1 hour before cutting into squares.