Preheat oven to 350 degrees. In a large ziplock bag pour 3 cups of crushed pretzels, and brown sugar into bag, close and shake well. Melt one stick of butter, open bag of pretzels and pour melted butter into bag. Reseal and shake well, coating all pretzels with melted butter. Empty pretzel mixture into 13x9 well greased deep dish cake pan and bake for 10 minutes at 350 degrees. Cool and set aside.
In a large mixing bowl combine 2 packages of softened cream cheese, 4 cups of powdered sugar, mix well. Slowly add 2 cups of milk, stir until completely mixed. Add 2 cups of peanut butter, mix well, finally, add thawed whipped topping. Mix everything well, mixture will be light and fluffy.
Add filling mixture over cooled pretzel crust, smooth evenly. Next, take your hot fudge and drizzle over filling, take your melted peanut butter and drizzle over filling, and then take your carmel sauce and drizzle over filling. Finally, top with crushed peanut butter cups. Freeze overnight.