I was certain I had ruined the entire batch the moment I realized what I’d done. Instead of reaching for vegetable oil, I had mixed a full cup of mayonnaise into my brownie batter, and as I stared at the bowl, I was already imagining a pan of inedible chocolate disaster, therefore
Thirty-five minutes later, the brownies emerged looking better than any I’d made before—crackly on top, rich in the center, and unbelievably moist. What seemed like a baking mistake turned into a surprising lesson about a secret ingredient that many experienced bakers have been quietly using for years, but