This OK chocolate cake is a straightforward cocoa cake made with buttermilk, oil, and hot coffee or water, then finished with a quick chocolate buttercream. The one-pan method makes a tender, moist cake that is easy to slice for a casual dessert, birthday table, or afternoon treat.
Ingredients
- 1 teaspoon (5 ml) neutral oil or softened butter, for greasing the pan
- 2 cups (250 g) all-purpose flour
- 1 3/4 cups (350 g) granulated sugar
- 3/4 cup (75 g) unsweetened natural cocoa powder
- 1 1/2 teaspoons (6 g) baking powder
- 1 1/2 teaspoons (7 g) baking soda
- 1 teaspoon (6 g) fine salt
- 2 large eggs, at room temperature if convenient
- 1 cup (240 ml) buttermilk
- 1/2 cup (120 ml) neutral oil, such as canola or sunflower
- 2 teaspoons (10 ml) vanilla extract
- 1 cup (240 ml) hot brewed coffee or hot water
- 1/2 cup (113 g) unsalted butter, softened, for the frosting
- 2/3 cup (57 g) unsweetened cocoa powder, for the frosting
- 3 cups (360 g) powdered sugar, sifted if lumpy
- 1/3 cup (80 ml) milk, plus up to 1 tablespoon (15 ml) more if needed
- 1 teaspoon (5 ml) vanilla extract, for the frosting
- 1/8 teaspoon (about 1 g) fine salt, for the frosting
Instructions
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Set a rack in the middle of the oven and heat it to 350°F (177°C). Grease a 9-by-13-inch (23-by-33-cm) baking pan. For easier lifting and cleanup, line the bottom with parchment paper after greasing; the paper is helpful but not essential. Measure the ingredients before you begin so the hot liquid can be added promptly once the batter is mixed.
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In a large bowl, whisk together the flour, granulated sugar, 3/4 cup cocoa, baking powder, baking soda, and salt. Break up any cocoa lumps with the whisk. This even distribution matters: pockets of baking soda can leave an unpleasant taste, while a clump of cocoa may remain dry in the finished cake.
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In a second bowl, whisk the eggs, buttermilk, oil, and 2 teaspoons vanilla until blended. Pour this mixture into the dry ingredients and stir with a whisk or sturdy spoon just until no large dry patches remain. The batter will be thick at this point. Avoid beating it for a long time; overmixing after the flour is added can make the crumb tougher.
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Pour in the hot coffee or hot water gradually while stirring. The batter will become thin and pourable, which is expected. Coffee deepens the chocolate flavor without making the cake taste strongly of coffee; use hot water if you prefer to avoid coffee altogether. Scrape the bowl once to make sure no dry flour is hiding at the bottom.
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Pour the batter into the prepared pan and smooth it into the corners. Bake for 32 to 35 minutes, turning the pan once only if your oven heats unevenly. Begin checking at 32 minutes: a toothpick inserted near the center should come out with a few moist crumbs, not wet batter, and the center should spring back lightly when touched. USDA FSIS gives 160°F (71°C) as the safe minimum internal temperature for egg dishes; if checking with an instant-read thermometer, the center should reach at least that temperature. Do not rely on a thermometer alone for cake texture, since a cake can be safe before it is fully baked through.
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Set the pan on a wire rack and let the cake cool in the pan for 60 minutes before frosting. The cake needs to be cool to the touch so the buttercream does not melt. If the kitchen is warm, give it a little extra time rather than frosting a warm center; the frosting can be made during the cooling period, but wait to spread it until the cake has cooled.
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To make the frosting, beat the softened butter in a bowl until smooth. Add the 2/3 cup cocoa and powdered sugar in a few additions, mixing on low so the sugar does not puff out of the bowl. Add the milk, 1 teaspoon vanilla, and 1/8 teaspoon salt, then beat until creamy. If it is too stiff to spread, add the extra milk a teaspoon at a time; if it seems loose, mix in a little more powdered sugar.
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Spread the frosting evenly over the cooled cake, working from the center toward the edges. A small offset spatula or the back of a spoon makes soft swirls without needing a piping bag. Cut into 12 portions with a clean knife, wiping the blade between cuts for neater edges. The recipe timing includes the 60-minute cooling wait; total elapsed time is about 2 hours.
Tips
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Measure flour lightly. Spoon flour into the measuring cup and level it with a straight edge instead of packing it down. Too much flour is a common reason chocolate cake turns dry or dense. For the most consistent result, weigh the flour if you have a kitchen scale.
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Use natural cocoa as written. This recipe pairs natural cocoa with baking soda, which helps the cake rise and gives it its familiar chocolate flavor. Dutch-process cocoa is less acidic and may change the rise and flavor, so it is not a one-for-one swap here. If that is all you have, use the variations section for a simple flavor adjustment rather than changing the leaveners at random.
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Buttermilk has a handy substitute. If you do not have buttermilk, stir 1 tablespoon (15 ml) lemon juice or white vinegar into a measuring cup, add milk to reach 1 cup (240 ml), and leave it for 5 minutes. The result is thinner and may be a little less tangy than cultured buttermilk, but it works well in this cake.
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Do not frost while warm. Even a slightly warm cake can soften buttercream and make it slide. If you are short on time, cool the pan on a rack in a draft-free spot; avoid putting a hot glass or metal pan straight into the refrigerator, where a sudden temperature change can affect the pan and the cake.
Serving Suggestions
Serve the cake at room temperature so the crumb is soft and the frosting is easy to cut. It is rich enough to stand on its own, but a spoonful of lightly whipped cream or a scoop of vanilla ice cream makes a simple plated dessert. Fresh strawberries, raspberries, or sliced pears add a bright, fruity contrast; use a small handful alongside each slice rather than piling wet fruit over the frosting well ahead of serving.
For a party, cut the cake into 12 generous pieces or 16 smaller squares. A warm, dry knife gives cleaner slices, and wiping it between cuts keeps frosting from dragging across the next piece. If you are serving the cake after a meal, take it out of the refrigerator about 20 to 30 minutes beforehand so it loses its chill without being left out for an extended time.
Variations
Make it more deeply chocolatey: Use hot coffee instead of water and add 1/2 cup (85 g) semisweet chocolate chips to the batter after adding the hot liquid. The chips settle somewhat in the thin batter, so fold them in briefly and bake right away. The finished cake will have little pockets of melted chocolate and a slightly sweeter bite.
Add a simple topping: Leave off the buttercream and dust the cooled cake with 1 tablespoon (8 g) powdered sugar, or spread the top with a thin layer of chocolate ganache. A ganache made with cream is perishable, so refrigerate a cake topped that way within 2 hours. For a less sweet finish, use unsweetened whipped cream when serving rather than changing the cake batter.
Use a different pan: Two 8-inch (20-cm) round pans can work for a layer cake. Grease and line both pans, divide the batter evenly, and start checking for doneness around 25 minutes; exact baking time depends on the pans and oven. Cool the layers completely before removing them and frosting. Do not fill the pans more than about two-thirds full; if you have extra batter, bake it separately in a small oven-safe dish.
Skip dairy in the batter: Use an unsweetened plant-based milk mixed with 1 tablespoon (15 ml) vinegar in place of buttermilk, and choose a plant-based butter and milk for the frosting. The cake will still be tender, though the frosting flavor and texture depend on the substitute butter. Check that the cocoa and sugar you choose suit your dietary needs, since products and labels vary.
Storage and Reheating
Because this cake has a milk-based frosting, refrigerate it within 2 hours of frosting or serving. Cover the pan tightly or move slices to an airtight container; it keeps well in the refrigerator for 3 to 4 days. The frosting firms when cold, so for the best texture let a slice sit at room temperature for about 20 to 30 minutes before eating. That gentle warming is usually preferable to reheating, which can melt the frosting unevenly.
To freeze the cake, chill it until the frosting is firm, then wrap individual slices or the whole cake tightly in plastic wrap and a layer of foil. Freeze for up to 2 months for best quality. Thaw wrapped portions in the refrigerator overnight, then unwrap after thawing to reduce condensation on the frosting. Do not leave the cake at room temperature for more than 2 hours; return uneaten portions to the refrigerator promptly.
Frequently Asked Questions
Can I make this cake without coffee?
Yes. Replace the hot coffee with the same amount of hot water. Coffee is there to bring out the cocoa flavor, not to make the cake taste like a coffee dessert. The water version is still chocolatey and tender, with a slightly less rounded flavor.
Why is my chocolate cake dry?
Common causes include measuring too much flour, baking longer than needed, or using a pan smaller than the one specified. Start checking at 32 minutes and take the cake out when the center is set and a toothpick shows moist crumbs. An oven thermometer can help if your oven runs hotter than its display suggests.
Can I make the cake ahead?
Yes. Bake it a day ahead, cool it completely, cover the pan, and refrigerate it. You can frost it once cool or frost it the next day; if the frosting has been refrigerated separately, let it soften slightly and beat it briefly before spreading. Store the finished cake covered in the refrigerator and allow a slice a short time to lose its chill before serving.
Can I mix the batter with a stand mixer?
You can, but a whisk and spoon are enough. If using a stand mixer, use the paddle attachment on low and stop as soon as the dry ingredients are incorporated. Add the hot liquid slowly to avoid splashing, and do not run the mixer at high speed after adding the flour.
How can I tell whether the cake is done without a thermometer?
Check the center with a toothpick or thin skewer: it should come out without liquid batter, though a few moist crumbs are fine. The surface should spring back lightly after a gentle touch, and the edges may begin to pull just slightly from the pan. If the skewer shows wet batter, bake for another 2 minutes and check again.
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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