I Was Skeptical—But This 1 Ingredient Changes the Boxed Brownie Game

I like my brownies made from scratch, without substitutions or “hacks,” that could potentially alter my favorite dessert. Since writing about food is my job, though, sometimes I’m asked to do things that make me uncomfortable. Like making my brownies from a mix…with mayonnaise. A double-whammy for this deeply passionate brownie connoisseur. Could mayonnaise really be used in place of the egg or oil as suggested by the internet? I set out to find out and here’s what happened.

Why Should You Put Mayonnaise In Brownies? 

I’m not the first one to discover that using mayonnaise in place of oil in brownie recipes works. Your grandparents, food bloggers and the bakers have been secretly dipping their spoons into jars of mayonnaise to create delicious baked goods for a while now. It’s a swap that makes sense since mayonnaise is made of mostly oil and egg. It provides moisture, which keeps the baked goods soft and tender, just like oil does. For most recipes, it’s a one-to-one substitution, and works in everything from cakes to muffins. 

I Tried Mayo Brownies

To keep things fair, I made two batches of brownies, both using the same box mix (Ghirardelli, because it’s the best). I made the control batch following the package directions, adding the water, oil and egg, as specified. For the test batch, I added the water and egg, but swapped an equal amount of mayonnaise (Duke’s) for the oil. I baked them both in 8-inch metal pans for 35 minutes, which was when the toothpick inserted in the center came out clean. I let them cool in the pan, then sliced them into squares for testing.

I tasted the control first and recognized the familiar flavors. The brownie tasted like it always does, fudgy and delicious. Next, I tried the mayo batch and I was surprised that I didn’t immediately taste a difference. While I was expecting a bit of tang (because mayo also contains vinegar and/or lemon juice), it’s not noticeable. All I could really taste was chocolate. I repeated the bites of both and had a similar experience. It was only after multiple tastes of the mayo-brownie that I began to detect a bit of that savory mayonnaise essence. It was just as fudgy as the OG brownie and just as flavorful.

Beyond flavor, I noticed that the mayonnaise brownies were a bit lighter in color, and that the tops were also shinier and had more crackling than the traditionally-made brownies. This made them look a little more impressive, and provided a fun paper-thin crisp bite. 

The Bottom Line 

You know how I feel about substitutions and hacks, but after adding mayonnaise to my brownies, I’m a changed woman. I enjoyed the results and appreciated the alternative for when I don’t have an egg or oil on hand. I don’t know that I’ll use mayonnaise to make all of my boxed brownies, but it’s nice to know I’ve got a back-up plan. Now it’s time to restock my mayo!