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My uncle hated coffee. He refused it at every table in the family for his whole life, made a face when he smelled it, and asked my mother for the recipe for her chocolate cake three separate times before she finally told him there was a full cup of coffee in the batter. He had already eaten two pieces. He ate a third one after she told him, which my mother considered the end of the argument.
Black magic cake is an old recipe that turned up in community cookbooks all over the country, and it earns its name. The batter is cocoa, sugar, flour, buttermilk, oil and eggs, and the last thing that goes in is a cup of hot, strong coffee. The batter turns so thin and runny that the first time you make it you will be sure something went wrong. It bakes into the darkest, most tender chocolate cake you have ever cut, moist enough that it stays soft for days. The hot coffee does two jobs. It blooms the cocoa, waking up the chocolate flavor so the cake tastes twice as chocolatey as the same recipe made with milk, and it makes a loose batter that bakes into a fine, damp crumb. What it does not do is make the cake taste like coffee. It tastes like chocolate, and that is all anybody ever notices.
Why this black magic cake works
- Hot coffee blooms the cocoa. Heat releases the flavor in cocoa powder, and coffee’s own roasted bitterness makes chocolate taste deeper. The coffee flavor itself disappears.
- A very thin batter. All that liquid turns into steam and moisture in the oven, giving a fine, damp, tender crumb.
- Oil instead of butter. The cake stays soft even when cold, and it keeps for days.
- Buttermilk and baking soda. The acid in the buttermilk reacts with the soda for a good rise and a slightly tangy, rich flavor.
Ingredients
Makes one 9 by 13 inch sheet cake, about 20 squares. The measurements are in US cups with grams in brackets.
For the cake
- 2 cups granulated sugar (400g)
- 1 3/4 cups all-purpose flour (220g)
- 3/4 cup unsweetened cocoa powder (65g)
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon fine salt
- 2 large eggs
- 1 cup buttermilk (240ml)
- 1/2 cup vegetable oil (120ml)
- 2 teaspoons vanilla extract
- 1 cup hot strong coffee (240ml)
For the frosting
- 1/2 cup unsalted butter (113g), melted
- 1/3 cup unsweetened cocoa powder (30g)
- 3 cups powdered sugar (360g)
- 1/3 cup milk (80ml)
- 1 teaspoon vanilla extract
Any brewed coffee works, regular or decaf, as long as it is hot and on the strong side. Day-old coffee reheated is exactly what most mothers used. If you have no coffee at all, a cup of boiling water makes a good cake, just not quite as dark.
How to make black magic cake
- Heat the oven to 350 degrees (175°C). Grease a 9 by 13 inch baking pan well, or grease it and line the bottom with parchment.
- In a large bowl, whisk together the sugar, flour, cocoa, baking soda, baking powder and salt until no lumps of cocoa remain.
- Add the eggs, buttermilk, oil and vanilla. Beat with a mixer on medium speed, or hard with a wooden spoon, for 2 minutes, until smooth and thick.
- Pour in the cup of hot coffee and stir on low speed or by hand until fully blended. The batter will be very thin, almost like soup. That is correct; do not add more flour.
- Pour the batter into the pan. Bake for 35 to 40 minutes, until the center springs back when touched and a toothpick comes out with only a few moist crumbs.
- Set the pan on a rack and let the cake cool completely in the pan, about 1 hour.
- For the frosting, stir the melted butter and cocoa together, then beat in the powdered sugar, milk and vanilla until smooth and glossy. Add a spoonful more milk if it is too stiff to spread. Spread over the cooled cake and cut into squares.
Tips that make the difference
- Sift or whisk the cocoa well. Cocoa lumps stay lumps in a thin batter.
- Do not overbake. Pull the cake when a toothpick shows a few moist crumbs; a perfectly clean toothpick means it has gone a little too far.
- Let it cool in the pan. This cake is very tender while warm and breaks if you try to turn it out.
- The cake is even better the next day, once the moisture has evened out through the crumb.
Variations
- Layer cake. Bake in two greased and lined 9 inch round pans for 30 to 35 minutes and double the frosting.
- Cupcakes. Fill lined muffin cups two-thirds full and bake 18 to 22 minutes. Makes about 24.
- No buttermilk. Stir 1 tablespoon of vinegar or lemon juice into 1 cup of milk and let it sit 5 minutes.
- Peanut butter frosting. Beat 1/2 cup creamy peanut butter into the frosting in place of the cocoa.
Storage and make-ahead
Keep the cake covered in its pan at room temperature for up to 4 days. It stays moist the whole time.
In warm weather keep it covered in the refrigerator and let squares come to room temperature before serving.
Unfrosted cake freezes well for 3 months, wrapped tightly in plastic and foil. Thaw in the wrapping and frost.
Frequently asked questions
Can you taste the coffee in black magic cake?
No. The coffee deepens the chocolate flavor, but the cake tastes of chocolate, not coffee. People who never drink coffee eat it without knowing.
Why is my batter so thin?
It is supposed to be. The cup of hot coffee makes a runny batter, and that is what gives the cake its moist, fine crumb.
Can I use decaf?
Yes. Decaf coffee works exactly the same.
Can I use butter instead of oil?
Melted butter works, but the cake will be a little firmer when cool. Oil keeps it softer for longer.
Pour in the hot coffee last, trust the thin batter, and let them eat two pieces before you tell them what is in it. That is the right order.
Black Magic Cake (Chocolate Cake with Hot Coffee)
The darkest, moistest chocolate sheet cake: cocoa, buttermilk and oil, with a cup of hot strong coffee poured into the batter last so it goes thin as soup. Baked at 350 degrees in a 9 by 13 pan with a fudgy cocoa frosting. Nobody tastes the coffee.
Ingredients
- 2 cups granulated sugar
- 1 3/4 cups all-purpose flour
- 3/4 cup unsweetened cocoa powder
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon fine salt
- 2 large eggs
- 1 cup buttermilk
- 1/2 cup vegetable oil
- 2 teaspoons vanilla extract
- 1 cup hot strong coffee
- 1/2 cup unsalted butter (113g), melted
- 1/3 cup unsweetened cocoa powder
- 3 cups powdered sugar
- 1/3 cup milk
- 1 teaspoon vanilla extract
Instructions
- Heat the oven to 350 degrees (175°C). Grease a 9 by 13 inch baking pan well, or grease it and line the bottom with parchment.
- In a large bowl, whisk together the sugar, flour, cocoa, baking soda, baking powder and salt until no lumps of cocoa remain.
- Add the eggs, buttermilk, oil and vanilla. Beat with a mixer on medium speed, or hard with a wooden spoon, for 2 minutes, until smooth and thick.
- Pour in the cup of hot coffee and stir on low speed or by hand until fully blended. The batter will be very thin, almost like soup. That is correct; do not add more flour.
- Pour the batter into the pan. Bake for 35 to 40 minutes, until the center springs back when touched and a toothpick comes out with only a few moist crumbs.
- Set the pan on a rack and let the cake cool completely in the pan, about 1 hour.
- For the frosting, stir the melted butter and cocoa together, then beat in the powdered sugar, milk and vanilla until smooth and glossy. Add a spoonful more milk if it is too stiff to spread. Spread over the cooled cake and cut into squares.
