Christina Tosi'S Christmas Treats - cooking recipe

Ingredients

4 tablespoons (1/2 stick) unsalted butter
4 cups mini marshmallows*
6 cups cereal (Rice Krispies, cornflakes, Golden Grahams, Kix, etc.)
Nonstick vegetable-oil spray
Up to 1 cup dried fruit, such as blueberries, cranberries, cherries, banana chips, or candied ginger, large pieces chopped or crushed
Up to 1 cup nuts or seeds, such as pecans, peanuts, walnuts, pepitas, or sunflower seeds, toasted and coarsely chopped
1/2 cup semisweet chocolate chips
1/4 cup creamy peanut butter (do not use natural or freshly ground; mix peanut butter into the melted-marshmallow mixture before adding cereal)
1 to 2 tablespoons sesame seeds
2 tablespoons sprinkles or other edible decoration
1/2 teaspoon ground spices, such as cinnamon or ginger
*To make this recipe, you'll need slightly less than 1 (16-ounce) bag of mini marshmallows. Snack on the extras or save them for hot cocoa.
9- by 13-inch baking pan, parchment or wax paper

Preparation

Spray a 9- by 13-inch baking pan with nonstick vegetable-oil spray.
In an extra-large saucepan over low heat, melt the butter. Add the marshmallows and heat, stirring constantly, until completely melted, about 2 minutes. (Add the peanut butter, if using, and stir to combine.) Remove from the heat, add the cereal and use a sturdy, long-handled wooden or metal spoon to stir until the cereal is well coated in the butter-marshmallow mixture. Add any optional mix-ins and stir to incorporate.
Scrape the mixture into the prepared pan and spread evenly. Cut a piece of parchment or wax paper into a roughly 9- by 13-inch rectangle and spray with nonstick vegetable-oil spray. Place the greased parchment or wax paper on top of the treats and press the mixture into the pan until it's 1/2 to 1 inch thick. Let cool until firm, 15 to 20 minutes.
Using a large, sharp knife cut the treats into approximately 2-inch squares. DO AHEAD: