Combine the butter and sugars in the bowl of a stand mixer fitted with a paddle attachment, and cream together on medium-high for 2 to 3 minutes. Scrape down 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 1 minute).

On low speed, paddle in the corn flake crunch and mini chocolate chips until they’re incorporated.

Divide dough into 1/4 c. balls, stuff with 2 mini marshmallows*, and line balls on a parchment-lined sheet pan. Refrigerate for at least 1 hour, or place in freezer for 30-45 minutes. (This step is critical! They must be chilled!)

Heat the oven to 365°f (original recipe calls for 375, but mine burned at this temp).

Re-arrange the chilled dough a minimum of 4 inches apart on parchment- or silpat-lined sheet** and bake for 11-16 minutes (check the cookies at 11 minutes). The cookies will puff, crackle, and spread. (The originals are more well-done than I prefer to make mine... so use your discretion!)

Cool the cookies completely on the sheet pans before transferring to a plate or airtight container for storage.

Pour the cornflakes in a medium bowl and crush them with your hands (or a cup since my hands felt like they were crushing glass after 30 seconds). Add the milk powder, sugar, and salt and toss to mix. Add the butter. As you toss, the butter will act as glue, binding the dry ingredients to the cereal and creating small clusters.

Spread the clusters on a parchment- or silpat-lined sheet pan and bake for 20 minutes, at which point they should look toasted, smell buttery, and crunch gently when cooled slightly and chewy.

Cool completely before storing or using in a recipe. (Stored in an airtight container at room temperature, the crunch will keep fresh for 1 week; in the fridge or freezer, it will keep for 1 month.)