Christina Tosi, the Founder of Milk Bar, on Her Collaboration With M&M’S (EXCLUSIVE)

“If your dough is too warm, your cookie usually spreads flat,” Christina said, which means that bakers should put the dough in the fridge. “If your dough bakes and doesn’t spread enough, it means that you don’t have the right ratio of fat to dry ingredients.”

When a baker isolates one cookie from the rest, there’s always a way to adjust before wasting an entire batch (and all of that hard work).

“If you bake a tester cookie, you always have the opportunity to tweak either what’s in the bowl or the temperature of it,” she continued.