1-First Step: Prep and pan Spray or grease a 9×13-inch baking pan with nonstick cooking spray or butter. Measure and line up all ingredients so everything melts and mixes quickly once the butter browns. Having tools ready will keep you from overcooking marshmallows.

2-Second Step: Brown the butter Place 2 sticks (226 grams) unsalted butter in a large stainless steel pan over medium-low heat. Use a stainless steel pan so you can watch color changes clearly. As the butter melts, it will foam and sizzle; keep an eye on it. After the popping stops, the milk solids will begin to color and brown bits will form. This process takes only about 2 to 3 minutes after the initial popping stops. You want a golden color and a nutty aroma, not a burned smell. When you see brown flecks and smell toffee notes, remove the pan from heat.

3-Third Step: Melt marshmallows and finish the base Immediately add 2 10-ounce bags mini marshmallows, 1 teaspoon vanilla extract, and 1/2 teaspoon kosher salt to the browned butter. Reduce heat to low and stir constantly until the marshmallows are melted and smooth. Be gentle and slow: melting on low heat prevents the mixture from becoming too stiff. If the marshmallows are fresh, they will melt into a glossy, flexible binder.

4-Fourth Step: Fold in the cereal Remove the pan from heat and stir in 9 cups (225 grams) crispy rice cereal until evenly coated. Work quickly but carefully so the mixture stays warm enough to bind, yet not so hot that it becomes sticky or brittle.

5-Fifth Step: Transfer and press Transfer the mixture into the prepared 9×13-inch pan. Press the mixture gently into an even layer using a spatula or lightly greased hands. Avoid packing the cereal tightly; light pressing keeps the treats soft and chewy. If you press too hard they become dense and firm.

6-Final Step: Cool and cut Let the tray cool at room temperature for 1 hour. Once set, cut into 12 squares. For neat cuts, use a sharp knife dipped in warm water and wiped dry between cuts. Serve at room temperature.