Chocolate Mayonnaise Cake

About This Recipe

While cakes and cookies aren't really my thing, I can absolutely get behind a simple mayonnaise cake. It's one bowl, minimum effort, and a sweet afternoon treat.

A Brief History Of Mayonnaise Cake

Mayonnaise cake became popular during the Great Depression in the 1930s. Since eggs and butter were expensive and hard to find, people used mayonnaise as a substitute because it’s made of eggs and oil. This helped keep cakes moist and flavorful, even without traditional ingredients. The concept has remained popular over time because it’s simple and tasty. Today, mayonnaise cake is a fun example of creative cooking!

What I Love About This Recipe

Simple, rich, and completely fermented. This recipe can be made all in one bowl over a scale. The mayonnaise keeps the cake incredibly moist and soft, while the instant espresso enhances the deep chocolate flavor. For those who care about what’s in their food, this cake doesn’t use any unfermented flour, making it a great option for sensitive eaters. Altogether, this cake will wow anyone who tries it, whether for a special occasion or just because.

All The "Why's"

Sugar

Without sugar, a cake would be dry, dense, and not very tasty. Sugar isn't just for a sweet flavor - it also helps trap moisture, air, and contributes to the Maillard reaction, which is responsible for making baked goods turn brown (although, this cake is already so dark, you probably wouldn't notice). It also balances out the bitterness of the cocoa powder and the instant espresso.

Leavening

I prefer chemical leavening for sourdough discard recipes because we are using starter that is not in its prime state, and may not rise well (especially in this recipe, where we don't add any flour). The truth is - without the baking soda, this dish would be much denser.

The baking soda reacts with the sourdough discard to leaven the batter: trapping carbon dioxide gases and creating bubbles which cause the batter to rise and become light and fluffy. It is the perfect match for a discard-heavy recipe like this one, since the acids in the discard allow the baking soda to do its work.

If your discard is on the older end, you'll notice it doesn't get too great of a rise. I do recommend using discard that is less than one month old, or that hasn't gone completely dormant and started producing hooch.

If needed, you can substitute one tablespoon of baking powder (which contains the acids needed to leaven the dish) for the baking soda.

Cocoa Powder

Cocoa powder is the source of chocolate in this chocolate mayonnaise cake. The more cocoa powder, the deeper the chocolate flavor becomes.

I find cocoa powder to be as difficult to measure by volume as flour. It can be helpful to spoon and level, or just weigh your ingredients.

Instant Espresso

A little bit of instant espresso can go a long way in enhancing the chocolate flavor, making it more intense and complex. It's a perfect pair. The coffee flavor itself doesn’t stand out but works to highlight and amplify the natural flavors of the cocoa.

Mayonnaise

We couldn't have a mayonnaise cake without mayonnaise, could we? Most cakes are made with eggs and oil; however, these ingredients were expensive during the Depression era. Mayonnaise, which is made of both eggs and oil, became the affordable substitute. The oil adds richness and keeps the cake from drying out, while the eggs provide structure and help bind the ingredients together. Mayonnaise also creates a smooth, velvety crumb, giving the cake a luxurious feel. Even though it’s a savory condiment, mayonnaise doesn’t add any strong flavor to the cake—it simply enhances its texture and keeps it fresh for longer.

What Kind Of Mayonnaise Should I Use?

Use a mayonnaise that doesn't include flavoring ingredients that do not pair well with cake (for example, onion powder). A simple mayonnaise should consist of eggs, oil, vinegar and/or lemon juice, salt, and maybe sugar. I use Hellman's/Best Foods mayonnaise in my mayonnaise cake. Here's the ingredient list:

Soybean Oil, Water, Whole Eggs and Egg Yolks, Distilled Vinegar, Salt, Sugar, Lemon Juice Concentrate, Calcium Disodium EDTA (Used to Protect Quality), Natural Flavors.

I do not recommend Miracle Whip for a couple reasons. First, it consists of more water than oil. A cake relies on oil and eggs, not water. Second, Miracle Whip contains mustard, spices, and dried garlic that don't necessarily pair well with cake.

Vanilla

Vanilla adds a sweet, warm, and slightly floral note that balances the sugar and other flavors, making the cake taste richer and more complete.

Sourdough Discard

Sourdough discard (extra, unfed sourdough starter) is the main ingredient this cake - the source of moisture and structure! The rule of thumb, well - my rule of thumb, based on my observations, is that the hoochier the discard, the less fluffy the bread made from it will be. Old, hooch-y discard does not leaven as well as fresher discard, producing a result that is not nearly as fluffy. However, the choice is yours!

It is important to note that with this much sourdough discard, your mayonnaise cake may or may not be sour. It all depends on your maintenance routine and the health of your starter. You can taste your discard (just a smidgen) before making this recipe - it'll tell you what the results might look like! I have made this recipe many times and have never had a sour outcome, while others cannot even imagine making a recipe like this because their discard is so sour. Sourness comes from the bacteria in your starter. When they overpopulate, you can taste it.

Mixing

Depending on the state of your discard, you may find mixing this batter difficult. I have tested this recipe with both broken down discard (almost hooch-y, but not quite) and newer discard where the gluten structure is still intact. While both come out well, and surprisingly neither noticeably affect the texture of the cake, it is easier to mix the batter with the broken down discard. If your discard is still fairly active or still has some gluten structure intact, I highly recommend using a handheld mixer with a dough hook attachment. I have a handheld KitchenAid mixer that works well, and I use these dough hook attachments (which are awesome because the discard does not climb up the hooks).

It is not possible to over-mix this batter. In fact, a good mix will only break down the structure of the discard even more. Mix it well and effectively.

Baking

With cake, low and slow baking is best. This helps to lock in moisture and to keep the edges of the cake from cooking too quickly. A toothpick inserted will tell you when it is finished.

📌 Quick Tip: Read the recipe in its entirety before you start cooking. This will help you understand the ingredients, steps, and timing involved, and allow you to prepare any necessary equipment or ingredients beforehand.