01 -
Set your oven temperature to 350°F and prepare a baking sheet by covering it with parchment paper.
02 -
Place the butter in a medium-sized pot over medium heat. Let it melt completely, then keep cooking as it bubbles and foams. Watch it closely and stir occasionally until you see it transform into a gorgeous amber color with a toasty, nutty aroma—this usually takes 5-7 minutes. Be attentive during this step since it can go from perfect to burned in seconds. Transfer the browned butter to a bowl and pop it in the refrigerator or freezer for roughly 10 minutes to bring it back to a workable temperature.
03 -
In a mixing bowl, combine your cooled brown butter with both the brown and white sugars. Mix them together, then crack in your egg and add the vanilla. Beat everything on low speed until you get a smooth, creamy mixture—about 30 seconds should do it.
04 -
Gently stir in the salt, baking soda, and flour. Mix just until everything comes together—don't overwork the dough or your cookies might turn out tough instead of tender.
05 -
Using a spatula or wooden spoon, gently fold the crispy rice cereal into the dough until evenly distributed. Then carefully fold in those mini marshmallows, trying to keep them intact.
06 -
Using a large cookie scoop (about 3 tablespoons), portion out the dough into generous balls. Arrange only 4 to 5 cookies per baking sheet, giving them plenty of room since these babies spread out quite a bit while baking.
07 -
Slide the baking sheet into your preheated oven and bake for 10 to 13 minutes. You're aiming for cookies that are lightly golden around the edges but still look slightly soft in the center. Don't let them get too dark or you'll lose that wonderful chewy texture. As soon as they come out of the oven, sprinkle them with flaky sea salt while they're still hot.