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Chocolate Mayonnaise Cake

A Depression-era cake that stays damp for four days. The mayonnaise is the eggs and the oil, and you will never taste it.

Prep
15 min
Cook
35 min
Makes
One 9-inch cake, 12 slices
Jump to the recipe
A square slice of frosted chocolate cake on a white plate
Photo: Veer Sajid / Pexels

The name puts people off, which is a shame, because the reasoning is sound and about a century old. Mayonnaise is an emulsion of oil, egg yolk and a little acid. A cake batter wants oil, egg and a little acid. Somebody in the 1930s, when eggs and butter were expensive and mayonnaise was not, worked out that you could use the jar instead of the components — and discovered the cake was better, because a pre-made emulsion disperses more evenly through flour than oil and egg added separately.

The result is a cake with an unusually fine, damp crumb that is still soft on day four. That is the whole appeal. No butter means no butter flavor, so the chocolate has to carry it: use good cocoa and bloom it in boiling water, which is the step that turns cocoa from dusty to deep.

Do not use light or reduced-fat mayonnaise. The fat is the point of it being there.

Nobody who eats this without being told will guess. Whether you tell them is your business.

For the other end of the chocolate spectrum — chewy rather than damp — see oatmeal chocolate chip cookies.

A spoonful of chocolate frosting beside scattered cocoa
Photo: congerdesign / Pixabay

An easy chocolate cake, printed

A Depression-era cake that stays damp for four days. The mayonnaise is the eggs and the oil, and you will never taste it.

Cake and frosting

For the cake

  • 2 cups (250 g) all-purpose flour
  • 1½ cups (300 g) superfine sugar
  • ¾ cup (65 g) cocoa powder
  • 1½ tsp baking soda
  • ½ tsp baking powder
  • ½ tsp fine salt
  • 1 cup (240 g) full-fat mayonnaise
  • 1 cup (240 ml) boiling water
  • 2 tsp vanilla extract

For the frosting

  • ½ cup (115 g) butter, softened
  • 2 cups (250 g) powdered sugar
  • ½ cup (40 g) cocoa powder
  • 3–4 tbsp milk
  • Pinch of salt

How to make a moist chocolate cake with mayonnaise

  1. 1 Heat the oven to 350°F (175°C) convection and line a 9-inch (23 cm) round cake pan. Whisk the flour, sugar, cocoa, baking soda, baking powder and salt together thoroughly — cocoa clumps, and lumps will not disperse later.
  2. 2 Stir the mayonnaise into the dry mix. It will look wrong: dry, stiff and unpromising. Keep going.
  3. 3 Pour in the boiling water and the vanilla and whisk until smooth. The water blooms the cocoa, which is where the depth of flavor comes from. The batter will be thin.
  4. 4 Pour into the tin and bake 32–35 minutes, until a skewer comes out with a few damp crumbs. Clean and dry means it has gone too far.
  5. 5 Cool in the tin 15 minutes, then turn out onto a rack and cool completely before frosting.
  6. 6 Beat the frosting ingredients together, adding milk a tablespoon at a time until it spreads easily.

Keeping and freezing

  • Full-fat mayonnaise only. Light versions are mostly water and the crumb collapses.
  • Keeps four days, covered, at room temperature — much longer than a butter cake, which is the reason the recipe survived.
  • It freezes well unfrosted, wrapped tightly, for three months.

The two questions everyone asks

No. There is no vinegar tang and no savoury note in the finished cake — the cocoa and sugar bury it completely, and what remains is the fat and the egg doing exactly what fat and egg do in any cake.

Cocoa contains flavor compounds that only dissolve properly at high temperature. Blooming it in boiling liquid is the single biggest difference between a cake that tastes brown and one that tastes of chocolate.