Lightly grease a 13x9” (33x23cm) baking dish with butter and set aside.
Brown the butter: Place butter in a large pot and heat over medium-low heat until melted. Once melted, increase heat to medium (or just a notch above medium) and cook the butter, swirling and stirring as it begins to bubble and pop. Once the bubbling and popping slows down you will notice brown bits forming on the bottom of the pan – congratulations, your butter is browned!
½ cup salted butter
Once butter is browned, turn heat to low and add marshmallows and vanilla extract, stirring gently until marshmallows are just melted.
10 oz marshmallows, ½ teaspoon vanilla extract
Remove pot from heat and cereal. Stir gently until cereal is evenly coated.
6 cups crisped rice cereal
Spread into prepared pan and cool 5-10 minutes before sprinkling with sea salt. Allow to cool completely before cutting and serving.
Sea salt
Notes
Butter
If you can get your hands on European-style butter (such as Kerrygold brand, this is butter with a butterfat content higher than 82%) this will make the treats taste even gourmet.
Storing
Once cooled, cover tightly with plastic wrap or store in an airtight container and store at room temperature for up to 3 days.