Our Chocolate Cake has a particular kind of reputation. People who have eaten it tend to
describe it the same way: darker than they expected, more intensely flavoured, and remarkably moist even days after baking. That last quality is the one that surprises people most. A dry chocolate cake is one of the great disappointments in baking. This one simply never is.
The reason is oil. Unlike our Vanilla Butter Cake, which relies on creamed butter for its structure and flavour, this recipe uses vegetable oil as its fat. Oil-based cakes stay moister longer because oil, unlike butter, does not solidify when cold. The result is a cake that has the same texture whether you eat it the day it is baked or two days later.
The other secret is the boiling water. Adding hot water to the batter blooms the cocoa powder — meaning it releases more of its flavour compounds — and produces that deep, almost roasted chocolate taste that makes this cake distinctive. It is a step that looks slightly alarming the first time you do it, because the batter becomes noticeably thin. Trust the process. This is correct. 
Method
A note on buttermilk: it is a key ingredient here, not a substitution for regular milk. Its acidity reacts with the baking soda to help the cake rise, and its slight tanginess balances the bitterness of the cocoa. If you do not have buttermilk, you can make a substitute by adding one tablespoon of white vinegar or lemon juice to 143 g of regular milk and letting it sit for five minutes.
1. Combine the oil and sugar in a mixing bowl and beat with an electric mixer until combined.
2. Add the egg and mix until incorporated.
3. In a separate bowl, whisk together the flour, cocoa powder, baking powder, baking soda and salt.
4. Combine the buttermilk and vanilla extract in a jug.
5. Alternate between adding the dry mixture and the buttermilk to the oil and sugar, starting and ending with dry. Scrape the bowl regularly.
6. Set the mixer to its lowest speed. Slowly pour in the boiling water in a thin, steady stream. Keep a firm grip on the bowl and be cautious — the steam is hot.
7. Stop the mixer just before everything looks fully combined and finish by hand. Do not
overmix.
8. Pour the batter (it will be quite liquid) into a greased and lined pan and tap to level.
9. Bake at 325 F (160 C) until a skewer comes out clean — about 25 minutes for a tall cake or 17 minutes for thinner layers.
10. Cool completely before removing from the pan. Wrap tightly and freeze for up to three
months.
- Use a good quality cocoa powder. The flavour difference between a standard supermarket cocoa and a higher-quality one is significant in a recipe this simple.
- The thin batter after adding the boiling water is expected. Do not be tempted to add more flour.
- This cake pairs well with American Buttercream, chocolate ganache, or a cream cheese frosting.
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The batter can also be baked in cupcake tins — fill two-thirds full and bake at 325 F for approximately 18 minutes
Final Thoughts
A chocolate cake that is genuinely moist, genuinely dark, and genuinely worth making again is something a baker should have in their collection. This is ours. It has been tested in our kitchen more times than we can count, and it has never once let us down. We hope it serves you just as well.
