One-Bowl Chocolate Cake With Easy Chocolate Frosting

By Warm Oven Bakes Editorial Team · Updated 1 November 2026

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Every baker needs one reliable chocolate cake. This one is mixed in a single bowl, needs no mixer for the batter, and stays moist for days thanks to oil and a hot liquid.

It works as a simple sheet cake for a holiday party, a two-layer birthday cake or a batch of cupcakes.

Why this cake is so moist

Oil instead of butter. Oil stays liquid at room temperature, so the cake stays soft even when chilled.

Hot coffee or water. Pouring a hot liquid over cocoa "blooms" it, releasing more chocolate flavor. Coffee deepens the chocolate taste without making the cake taste of coffee. Hot water works too.

A thin batter. The batter is very runny. That's normal, and it's what gives the tender crumb.

Ingredients

Makes one 9x13-inch cake or two 9-inch round layers:

• 1 3/4 cups (220 g) all-purpose flour
• 2 cups (400 g) granulated sugar
• 3/4 cup (65 g) unsweetened cocoa powder
• 1 1/2 tsp baking soda
• 1 1/2 tsp baking powder
• 1 tsp fine salt
• 2 large eggs, room temperature
• 1 cup (240 ml) milk, room temperature
• 1/2 cup (120 ml) neutral oil, such as vegetable or canola
• 2 tsp vanilla extract
• 1 cup (240 ml) hot brewed coffee or very hot water

Easy chocolate buttercream

• 1 cup (226 g) unsalted butter, softened
• 3 1/2 cups (420 g) powdered sugar
• 2/3 cup (55 g) unsweetened cocoa powder
• 1/4 tsp fine salt
• 1/3 cup (80 ml) milk or cream
• 2 tsp vanilla extract

Instructions

1. Heat the oven to 350°F (175°C). Grease a 9x13-inch pan, or grease two 9-inch round pans and line the bottoms with parchment.
2. Whisk the dry ingredients. In a large bowl, whisk the flour, sugar, cocoa, baking soda, baking powder and salt until there are no lumps of cocoa.
3. Add the wet ingredients. Add the eggs, milk, oil and vanilla. Whisk for about 1 minute until smooth.
4. Add the hot liquid. Slowly whisk in the hot coffee or water. The batter will be thin.
5. Bake. Pour into the pan(s). Bake a 9x13 cake for 35 to 40 minutes, or 9-inch layers for 30 to 35 minutes, until a toothpick in the center comes out with a few moist crumbs and the top springs back when lightly pressed.
6. Cool. Cool the 9x13 cake in the pan on a rack. For layers, cool in the pans for 10 minutes, then turn them out onto a rack to cool completely.

Making the buttercream

1. Beat the butter for 2 minutes until creamy.
2. Sift in the powdered sugar and cocoa, add the salt, and beat on low until combined.
3. Add the milk and vanilla and beat on medium-high for 2 to 3 minutes until fluffy. Add more milk a teaspoon at a time if it's too thick.

Frost only when the cake is completely cool, or the buttercream will melt. An offset spatula makes spreading much easier, and a cake turntable helps with layer cakes.

Cupcakes

Fill lined muffin cups about two-thirds full and bake at 350°F for 18 to 22 minutes. Makes about 24 cupcakes.

Tips for the best chocolate cake

Use room-temperature eggs and milk. Cold ingredients make a lumpier batter and can affect the rise.

Don't overbake. Start checking 5 minutes early. A few moist crumbs on the toothpick is perfect; a completely clean toothpick can mean a dry cake.

Measure the flour correctly. Too much flour makes a dry, dense cake. See how to measure flour correctly.

Level the layers. If the layers dome, trim the tops with a serrated knife before stacking.

Holiday variations

• Peppermint: add 1/2 tsp peppermint extract to the frosting and top with crushed candy canes.
• Mocha: dissolve 1 tsp instant espresso in the milk for the frosting.
• Orange: add 1 tbsp finely grated orange zest to the batter.

Storage

• Frosted cake keeps at room temperature, covered, for 1 day, or in the fridge for up to 5 days. Bring to room temperature before serving for the best texture.
• Unfrosted layers can be wrapped and frozen for up to 3 months. Thaw in the wrapping, then frost.

Choosing the right pan

The pan changes the baking time more than anything else, so check early.

• 9x13-inch metal pan: 35 to 40 minutes. Easiest option for parties; frost and serve straight from the pan.
• Two 9-inch rounds: 30 to 35 minutes. Line the bottoms with parchment so the layers release cleanly.
• Three 8-inch rounds: 25 to 30 minutes. Taller, thinner layers that bake quickly.
• Glass 9x13 dish: works, but glass holds heat. Check from 30 minutes and consider lowering the oven to 325°F (165°C).

Fill pans no more than about two-thirds full. Overfilled pans can overflow, because this batter rises well.

How to tell when it's done

Look for three signs together: the top springs back when pressed lightly in the center, the edges are just starting to pull away from the pan, and a toothpick comes out with a few moist crumbs. Wet batter on the toothpick means it needs a few more minutes.

Read next: Soft Dinner Rolls for Holiday Dinners (Make-Ahead Option) →