Combine the marshmallows and butter in a large, microwave-safe bowl.
Heat in the microwave for 1½ to 2 minutes. The marshmallows will puff up quite a bit.
Stir until it becomes a nice, smooth consistency. If the marshmallows aren't quite melted, you can cook an additional 10-15 seconds.
Once smooth, stir in the cereal and salt. Stir well to coat all of the cereal evenly.
Spread it out into the prepared pan. Press into an even layer - you want to press semi-firmly but not so much that it makes them hard once they cool. Just enough to let them hold together but still be soft and chewy.
For Brown Butter Sea Salt Rice Krispie Treats
Start by lining a pan with parchment paper. Set aside for now.
In a large pot, begin to melt butter over medium heat. (Do not walk away from the pot. The butter can burn quickly). It should begin to melt, foam, then turn to a light brown color, with a very nutty, delicious aroma.
Turn off heat and stir in ½ tsp of salt & the marshmallows. Keep stirring to melt the marshmallows.
Once you have a smooth consistency and the marshmallows are completely melted. Stir in the cereal.
Spread the mixture into your prepared pan, pressing down into an even layer. Take care to not press too firmly or they will be too firm and not soft and chewy.
Top with remaining ½ tsp of sea salt. Let cool, then cut into squares.