Preheat oven to 350° and lightly spray a 9×13 pan with cooking spray.

In a large bowl combine crushed pretzels, melted butter, and brown sugar. Stir to combine.

Press mixture into prepared pan, packing tightly.

Bake for 10-12 minutes until lightly golden. Cool completely.

In a large mixing bowl beat peanut butter and room temperature butter together until smooth. Slowly add in powdered sugar, beating until incorporated. Spread on top of cooled crust. Chill until ready to spread caramel.

In a medium heavy saucepan combine granulated sugar, corn syrup, salt, and water. Bring mixture to a boil without stirring until temperature reaches 340° on a candy thermometer. Remove from heat and immediately add heavy cream, butter, and sour cream. Stir until combined and set aside to cool. When cool, stir in chopped peanuts and spread on top of peanut butter layer.

Melt milk chocolate and heavy cream in a double boiler or microwave until melted. Spread over caramel layer.

Chill until ready to cut into squares.