In a medium saucepan over low heat, melt down peanut butter, marshmallows, and butter. Stir until well combined and mostly smooth.
Meanwhile, trim fat from cooked bacon and chop into small pieces. Set aside.
Pour liquid mixture into a large mixing bowl with Rice Krispies and stir until cereal is evenly coated. Add bacon and stir until distributed throughout.
Lightly coat a glass baking dish with cooking spray. Scoop Rice Krispie Treat mixture into the dish, spread, and gently pat to even the top surface. Allow to set for 1-2 hours. (This process can be expedited by setting in the fridge).
Notes
We used a 13″ x 9″ baking dish; for thicker treats, try using an 11″ x 7″ baking dish.
For easy cutting and serving, line baking dish with parchment paper to prevent sticking.
Try adding 1/2 or 1 cup mini marshmallows (not melted) to the final mixture along with bacon for extra marshmallow-y flavor.