Line a rectangular baking dish (mine was 8x11 but a 8x8 or 9x9 pan will work too, you'll just have different sized treats) with wax paper.

Brown butter (tutorial link in notes section below) in a large sauce pan over medium heat, stirring frequently, until a nutty flavor develops, and golden bits form on the bottom of the pan (butter will first melt, then foam, then turn clear-ish golden, then start to brown and smell super nutty).

Reduce heat to low then stir in marshmallows, continuing to stir until marshmallows are smooth and fully incorporated with the brown butter. Remove mixture from heat. Stir in sea salt, white chocolate chips, rice krispy cereal, and heart sprinkles then mix using your hands or rubber spatula until well combined and chocolate is melted.

Spread mixture into prepared pan using your fingers or rubber spatula, making sure to fill in the corners all the way. Sprinkle a few dashes of red sugar sprinkles on top. Let cool then cut into rectangles, squares, or whatever shape your heart desires!