A chocolate cake with no eggs, no dairy and no nuts, using a cup of sourdough discard and a cup of boiling water.

Two nine inch rounds. The source gives no times or servings in any field, so those here are estimated from the method: roughly fifteen minutes of preparation, thirty to forty minutes of baking, and twelve servings from a two layer cake.

Boiling water goes in last

A cup of it, or hot coffee, and this is the technique that defines a good chocolate cake.

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Cocoa powder contains flavour compounds that are not fully released by mixing alone. Hot liquid blooms them, the same way hot water opens up ground coffee, and the result is a noticeably deeper chocolate flavour.

It also thins the batter considerably. This will look alarmingly runny before it goes in the pans, and that is correct. A thin batter bakes into a moist tender crumb.

Coffee instead of water pushes the chocolate further still. It does not taste of coffee at this quantity.

Discard rather than active starter

A cup, and inactive is specified.

The lift here comes entirely from two teaspoons of baking powder and a teaspoon and a half of baking soda. The starter is not doing any leavening, which is why discard works.

What it contributes is acidity and a faint tang that cuts through two cups of sugar, plus moisture and some body.

That acidity also feeds the baking soda, which needs an acid to react with.

Applesauce instead of eggs

Two thirds of a cup, unsweetened.

Eggs in a cake provide moisture, fat and structure. Applesauce covers the moisture and adds pectin, which gives a little binding, and the oil covers the fat.

Structure is the part that has no direct replacement, which is why this cake is denser and more fudgy than a conventional one. The recipe describes it as balanced between fudgy and fluffy, which is fair.

Unsweetened matters. There are already two cups of sugar here.

Grease and flour, do not just grease

Butter then a sprinkle of flour, which the recipe specifies.

An egg free batter has less protein to set against the pan, and it sticks more readily than a conventional cake. Flour over the greased surface gives a dry barrier that releases cleanly.

For a fully dairy free version, use oil or vegan butter for greasing.

Five minutes in the pan, then out

Before cooling fully on a rack.

Five minutes lets the crumb firm enough to survive being turned out. This cake is fragile while hot, more so than an egg based one.

Longer than that and steam condenses against the pan, making the bottoms wet.

Frost only when completely cool

Which the recipe emphasises and it is worth repeating.

Any frosting on a warm cake melts and slides. With a cake this moist there is also a risk of the layers compressing under the weight.

Shop-bought chocolate frosting works and the recipe suggests it, noting that some are incidentally free of dairy. Check the label rather than assuming, since formulations differ between brands and change over time.

What the discard is doing for flavour

Sourdough discard is fermented flour and water, and fermentation produces lactic and acetic acids.

In a chocolate cake that acidity does two things. It sharpens the cocoa, in the same way a pinch of salt does, and it balances a large quantity of sugar so the cake does not read as flatly sweet.

A week old discard from the fridge is more sour than a freshly fed one and gives a more noticeable tang.

Storing

Three days at room temperature covered, or five refrigerated. <p>It stays moist longer than most cakes thanks to the applesauce and the oil, both of which hold water better than butter does. ## Making it a sheet cake The batter fits a 9×13 pan, and the bake time goes to about 35 to 45 minutes. Test from 35 minutes.

That is the easier option if you do not want to frost a layer cake, and it makes the cake considerably more portable.

Using up discard

A cup is a substantial amount, which is what makes this recipe useful. Anyone maintaining a starter produces discard at every feeding, and there are limits to how many pancakes a household wants.