Prepare a 9x9 baking dish by first spraying with non-stick spray, then lining with 2 pieces of parchment paper to create a "sling" (You will cross these over each other) and then spray again lightly with non-stick spray.
In a large pot melt the butter and peanut butter together.
Then, add in the marshmallows and vanilla, stir continuously allow them to fully melt.
Next, fold in you Rice Krispie cereal and continue doing so until it is covered evenly. Be gentle, as to not crush the cereal.
Pour your warm Rice Krispie mixture into your prepared baking pan and press down lightly.
Top with flaky sea salt and press down gently again so that it sticks.
Place your treats in the fridge for 1+ hours until firm.
To cut, spray a large knife with non-stick spray and cut into 9 squares. May cut into smaller bars, if desired.
Enjoy!