Chocolate Cake Day

What the day is

Chocolate Cake Day is observed on January 27. Chocolate cake is a young dish. Cocoa was a drink in Europe for centuries before anyone put it in a cake, and that only became practical once the press of 1828 made dry cocoa powder available.

Origin and background

Nearly every good recipe involves pouring something hot into the batter, usually coffee or boiling water, and it is not there for warmth or to make the cake taste of coffee. Cocoa powder contains a great many flavor compounds locked into solid particles, and hot liquid dissolves and disperses them in a way cold liquid does not. The effect is called blooming, and it deepens chocolate flavor noticeably. Coffee is used because its own compounds reinforce the bitter, roasted notes already present, which is why a properly made chocolate cake tastes more chocolatey rather than tasting of coffee.

The second variable is acidity, and it explains the strange instructions in old recipes. Natural cocoa is acidic, so it reacts with baking soda to produce lift. Dutched cocoa has been treated with alkali, so it does not, and needs baking powder instead. Swapping one for the other without changing the raising agent produces a flat or soapy cake, which is the most common failure in chocolate baking.

Devil's food cake descends directly from this chemistry: the soda raises the pH of the batter, which deepens the color toward reddish brown, and red velvet is the same reaction seen before modern cocoa processing made it rare.

Fat matters more than in most cakes, because the cocoa solids are drying. Oil-based recipes stay moist for longer than butter ones, which is why the best keeping cakes use oil.

How to take part

• Bloom the cocoa in hot coffee or water, which costs nothing and changes everything.
• Match the cocoa to the raising agent: natural with soda, Dutched with powder.
• Use oil rather than butter if the cake needs to last more than a day.
• Add salt, and more than feels right.
• Underbake very slightly and let it cool fully before cutting.