Preheat the oven to 265 degrees. Line a baking sheet with parchment paper or a silicone baking mat; set aside.
Pour the cornflakes into a medium bowl. Crush the cornflakes to one-quarter of their original size. Add sugar and salt toss to combine. Add butter and toss again until the cornflakes are in small clusters.
Spread the cornflake mixture in an even layer on a parchment covered baking sheet. Bake until the clusters are toasted, about 20 minutes. Remove and let cool completely.
Cornflake Chocolate Chip Marshmallow Cookies
Combine the butter and sugars in a stand mixer with a paddle attachment, cream together on medium-high for 2 to 3 minutes. Scrape the sides of the bowl, add the egg and vanilla, and beat for 7 to 8 minutes.
Reduce the mixer speed to low and add the flour, baking powder, baking soda, and salt. Mix just until the dough comes together - no longer than a minute.
On low speed, paddle in the cornflake crunch and chocolate chips until they’re incorporated.
Divide dough into ¼ c. balls, stuff with 2 or 3 mini marshmallows, and place balls on a parchment-lined cookie sheet. Refrigerate for at least an hour, or place in freezer for 30-45 minutes. (Dough must be chilled!)
Heat the oven to 365°f
Re-arrange the dough balls minimum 4 inches apart on parchment- or silpat-lined cookie sheet and bake for 11-16 minutes (check the cookies at 11 minutes, mine took 12!) The cookies will puff, crackle, and spread.
Cool the cookies completely on cookie sheets before transferring to a plate. Store in airtight container.
Notes
Pro Tips: Dough must be chilled. Freeze balls of dough and then put them in the oven still frozen.Bring butter and eggs to room temperature before you mix them in.Store in an airtight container.