Instructions

Combine the butter, sugar, and glucose in the bowl of a stand mixer fitted with the paddle attachment and cream together on medium-high for 2 to 3 minutes. Scrape down the sides of the bowl, add the egg, vanilla, and melted chocolate, and beat for 7 to 8 minutes.

Reduce the mixer speed to low and add the flour, cocoa powder, baking powder, baking soda, and salt. Mix just until the dough comes together, no longer than 1 minute. (Do not walk away from the machine during this step, or you will risk overmixing the dough.) Scrape down the sides of the bowl with a spatula.

Still on low speed, add the chocolate crumbs and cornflakes and mix just until incorporated, about 30 seconds. You can preserve some of the cornflakes out if you’d like to use them to sprinkle on top of your cookies.

Using a 2 3/4-ounce ice cream scoop (or a 1/3-cup measure), portion out the dough onto a parchment-lined sheet pan. Pat the tops of the cookie dough domes flat. Wrap the sheet pan tightly in plastic wrap and refrigerate for at least 1 hour, or up to 1 week. Do not bake your cookies from room temperature–they will not bake properly.

Heat the oven to 375°F.

Arrange the chilled dough a minimum of 4 inches apart on parchment- or Silpat-lined sheet pans. Bake for 18 minutes. The cookies will puff, crackle, and spread. It’s tough (kind of impossible) to gauge if a cookie that is this dark with chocolate is done. If after 18 minutes, the cookies still seem doughy in the center, give them another 1 minute in the oven, but not more.

Cool the cookies completely on the sheet pans before transferring to a plate or an airtight container for storage. At room temp, the cookies will keep fresh for 5 days; in the freezer, they will keep for 1 month.