Line a 9x13-inch pan with parchment paper, allowing some to hang over on the sides. Set aside.

In a heavy bottomed pot over medium heat, melt the butter. Stir the butter the entire time. Once it has melted, the butter will foam and sizzle around the edges a bit.

Continue to stir the butter. The butter will turn a golden brown color. Some of the foam will have subsided and the milk solids at the bottom of the pan will be a toasty brown. It will smell very buttery and nutty.

Once it reaches this state, immediately add the peanut butter and stir to combine.

Add the marshmallows and stir until everything is well combined. Add the vanilla extract and flaky sea salt.

Turn off the heat and the rice cereal to the pot. Stir until all of the cereal has been coated in the peanut butter and marshmallow mixture.

Add the reserved marshmallows and the peanut butter chips. Stir until they are evenly distributed throughout the cereal.

Pour the cereal mixture into the prepared pan. Lightly press it down in an even layer.

Allow the treats to cool for about an hour before slicing and eating.