To the bowl of a stand mixer fitted with the paddle attachment (or large mixing bowl and electric mixer) add the egg, butter, sugars, vanilla, and beat on medium-high speed until creamed and well combined, about 4 minutes.

Stop, scrape down the sides of the bowl, and add the flour, oats, baking soda, salt, and beat on low speed until just combined, about 1 minute.

Stop, scrape down the sides of the bowl, and add the chocolate chips, Cornflakes, coconut, pecans, and beat on low speed until just combined, about 1 minute.

Using a large cookie scoop, 1/4-cup measure, or your hands, form 12-14 equal-sized mounds of dough.*

Place mounds on a large plate or tray, cover with plastic wrap, and refrigerate for at least 2 hours, up to 5 days. Do not bake with unchilled dough because cookies will bake thinner, flatter, and be more prone to spreading.

Preheat oven to 350F, line a baking sheet with a Silpat or spray with cooking spray. Place dough mounds on baking sheet, spaced at least 2 inches apart (I bake 8 cookies per sheet) and bake for about 10 to 12 minutes (11 minutes in my oven is just right), or until edges have set and tops are just set, even if slightly under cooked, pale, and glossy in the center; don’t over bake. Cookies firm up as they cool.