Step 1

Line a 9-by-13-inch baking dish with aluminum foil, leaving a 2-inch overhang on each of the longer sides. Spray the foil lightly with cooking spray.

Step 2

Melt the butter in a large pot over medium heat. Add the marshmallows and cook, stirring occasionally, until melted and smooth, about 5 minutes. Remove from the heat and stir in the vanilla and salt.

Step 3

Working quickly, add the rice cereal to the pot and stir with a rubber spatula until evenly coated. Transfer to the prepared baking dish and press into an even, compact layer. (Spray your hands with a little cooking spray to keep them from sticking when pressing the cereal mixture into the pan). Decorate with toppings if using (see Cook's Note).

Step 4

Let sit at room temperature until firm, about 30 minutes. Cut into 24 squares. Store the cereal treats at room temperature in an airtight container for up to 3 days.