Equipment
Ingredients
Dry Ingredients
- 190 g all-purpose flour
- 200 g granulated sugar
- 45 g dutch-processed cocoa powder
- 5 g baking soda
- 2 g baking powder
- 3 g salt
Wet Ingredients
- 225 g full-fat mayonnaise
- 5 ml vanilla extract
- 240 ml water, boiling
Mix-ins
- 85 g bittersweet chocolate, coarsely chopped
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 450 kcal
- Protein
- 4 g
- Carbohydrates
- 52 g
- Fat
- 26 g
- Fiber
- 4 g
- Sugar
- 29 g
- Sodium
- 525 mg
- Saturated Fat
- 6 g
- Trans Fat
- 0 g
- Monounsaturated Fat
- 5 g
- Polyunsaturated Fat
- 13 g
- Cholesterol
- 12 mg
- Potassium
- 118 mg
- Calcium
- 32 mg
- Iron
- 2.7 mg
- Magnesium
- 34 mg
- Phosphorus
- 78 mg
- Zinc
- 0.6 mg
- Vitamin A
- 7 mcg
- Vitamin D
- 0.1 mcg
- Vitamin E
- 0.9 mg
- Vitamin K
- 46 mcg
- Vitamin B6
- 0.0 mg
- Vitamin B12
- 0.0 mcg
- Thiamin
- 0.04 mg
- Riboflavin
- 0.04 mg
- Niacin
- 0.4 mg
- Folate
- 9 mcg
- Water
- 39 g
- Alcohol
- 0 g
- Caffeine
- 13 mg
Sources: Aggregated Public Data, USDA FoodData Central
Method
Preheat the oven to 175 degrees Celsius (350 degrees Fahrenheit). Lightly grease a 9-inch round cake pan and line the bottom with parchment paper.
In a large mixing bowl, thoroughly whisk together the all-purpose flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt until completely uniform.
Add the full-fat mayonnaise and vanilla extract to the dry ingredients. Stir with a spatula until a thick, somewhat dry paste forms.
Carefully and gradually whisk the boiling water into the thick batter. Stir slowly at first to avoid splashing, then whisk until the batter is completely smooth and glossy.
Gently fold the coarsely chopped bittersweet chocolate into the warm batter, distributing it evenly.
Pour the batter into the prepared cake pan. Bake for 30 to 35 minutes.
Remove from the oven and let the cake cool in the pan for 10 minutes. Turn it out onto a wire rack to cool completely before frosting or serving.
Chef's Notes
- Full-fat mayonnaise is crucial here; it acts as a perfect emulsion of vegetable oil and egg yolks, providing the cake's signature tender crumb without needing to cream butter and sugar.
- Using boiling water blooms the cocoa powder instantly, releasing flavor compounds that give the cake a much richer, darker chocolate profile.
- If you want to elevate the flavor further, swap the boiling water for freshly brewed hot espresso or strong coffee. It will enhance the chocolate notes without making the cake taste like coffee.
- Because this cake is intensely moist and has a delicate crumb, ensure it is completely cooled before applying any frosting, otherwise it may tear.
Storage
Refrigerator: 5 days — Store in an airtight container to maintain moisture.
Freezer: 3 months — Wrap tightly in plastic wrap and aluminum foil before freezing.
Troubleshooting
Cake texture is dense, gummy, or flat
Cause: Using low-fat mayonnaise, omitting the baking soda, or overmixing the batter once the hot liquid was added
Fix: Cannot be fixed, but can be repurposed into cake truffles or mixed with frosting.
Prevention: Always use real, full-fat mayonnaise which correctly replaces the oil and eggs. Whisk only until the batter is just smooth.
Batter looks incredibly thin and watery
Cause: Adding the boiling water all at once or measuring the liquid incorrectly
Fix: Continue whisking vigorously until the batter comes together. It will naturally be somewhat thin, which is expected.
Prevention: Measure liquids accurately and add the hot water in a slow, steady stream while whisking to create a proper emulsion.
Cultural Context
Originating during the Great Depression when dairy, fresh eggs, and butter were scarce and expensive, mayonnaise cakes became a resourceful American staple. The commercial emulsion of oil and eggs found in mayonnaise provides an ideal, ready-made fat base that yields incredibly tender baked goods, remaining a beloved and nostalgic birthday tradition in many households today.
