Line 2 large baking sheets with parchment paper or silicone baking mats. Lightly grease a large spoon or rubber spatula with nonstick spray, and have additional spray or a little softened butter ready to grease your hands for shaping.

In a large, heavy-bottomed pot (such as a Dutch oven), melt the 1/2 cup unsalted butter over low to medium-low heat. Do not brown the butter; keep the heat gentle so the mixture stays light in color.

Add the 10 oz bag of mini marshmallows to the melted butter. Stir constantly with the greased spatula over low heat until the marshmallows are fully melted and smooth, 3–5 minutes. Avoid overheating; remove the pot from the heat as soon as the mixture is smooth.

Turn off the heat. Stir in the vanilla extract and fine sea salt until evenly combined. Add green food coloring, starting with about 10 drops liquid (or a small amount of gel), and mix well. Add more coloring as needed until the mixture reaches a bright holly-leaf green, remembering it will lighten slightly once the cornflakes are added.

Pour about half of the 6 cups of cornflakes into the green marshmallow mixture. Gently fold to coat, then add the remaining cornflakes and continue folding until all flakes are evenly coated with no dry spots. Work quickly, as the mixture will firm up as it cools. If it seems too wet and won’t hold its shape, fold in an additional 1/2–1 cup cornflakes.

Using a greased spoon or a medium cookie scoop, drop mounds of the warm mixture onto the prepared baking sheets, using about 2–3 tablespoons per mound depending on how large you want each wreath.

Lightly grease your fingers with butter or nonstick spray. Working with one mound at a time, gently flatten it slightly, then use your thumb or the back of a small measuring spoon to make a hole in the center. Push the mixture outward to form a ring or wreath shape. They do not need to be perfectly round—slight irregularities add to the homemade look.

While the wreaths are still warm and sticky, press 2–4 red cinnamon candies, mini M&M’s, or red sugar pearls into each wreath to resemble holly berries. Add holiday sprinkles if desired. If candies slide off, wait a minute for the mixture to cool slightly, then press them back on.

Let the cornflake wreaths sit at room temperature on the baking sheets for 30–45 minutes, or until they are firm enough to pick up but still soft and chewy in texture.

Once set, gently lift the wreaths from the parchment and arrange them on a serving platter, cookie tray, or in gift boxes. Store in an airtight container at cool room temperature for 3–4 days, separating layers with parchment or wax paper.