Moist Chocolate Cake with Chocolate Buttercream

Some cakes are good, and some cakes never last long. This chocolate cake is definitely the second kind.

Made with cocoa powder, a mix of caster sugar and light brown sugar, and a splash of hot water for extra moisture, this cake bakes up beautifully soft and rich without being heavy. The batter is thin, which may feel surprising at first, but that’s exactly what helps create a tender, moist crumb.

To finish, the cake is covered with a creamy chocolate buttercream frosting made with unsalted butter, icing sugar, cocoa powder, milk, and vanilla. It’s smooth, chocolatey, and perfect for spreading between layers or over the top and sides.

Whether you’re baking for a birthday, a special occasion, or just because you fancy a proper homemade chocolate cake, this recipe is a lovely one to keep.

• Servings: 10–12 slices

• Prep: 25 minutes

• Cook: 30–35 minutes

• Cooling & Decorating: 1 hour+

• Total: About 2 hours

Ingredients

For the Chocolate Cake

220 g plain flour (1 3/4 cups all-purpose flour) 70 g unsweetened cocoa powder (3/4 cup) 2 tsp baking powder 1 tsp bicarbonate of soda (baking soda) 1/2 tsp salt 250 g caster sugar (1 1/4 cups granulated sugar) 100 g light brown sugar (1/2 cup packed) 2 eggs 120 ml vegetable oil (1/2 cup) 240 ml whole milk (1 cup) 180 ml hot water (3/4 cup) 2 tsp vanilla extract

For the Chocolate Buttercream Frosting

300 g unsalted butter (1 1/3 cups) 440 g icing sugar (3 1/2 cups powdered sugar) 60 g cocoa powder (1/2 cup) 3–4 tbsp milk 1 tsp vanilla extract

Instructions

1. Prepare the Cake Tins

Preheat the oven to 180°C / 350°F or 160°C fan.

Grease and line your cake tin or tins with baking paper. You can use two round cake tins for a layered cake, or one deeper tin if preferred. If using one deep tin, the baking time may be longer.

2. Mix the Dry Ingredients

In a large mixing bowl, whisk together the plain flour, cocoa powder, baking powder, bicarbonate of soda, and salt.

Add the caster sugar and light brown sugar, then whisk again until everything is evenly combined. Breaking up any lumps in the brown sugar will help the batter mix smoothly.

3. Add the Wet Ingredients

Add the eggs, vegetable oil, whole milk, and vanilla extract to the dry ingredients.

Mix until the batter is smooth and no dry patches remain. You can do this with a hand whisk, electric mixer, or stand mixer on low to medium speed.

4. Add the Hot Water

Carefully pour in the hot water and mix again until fully combined.

The batter will look thin and pourable — this is completely normal. The hot water helps bloom the cocoa powder, giving the cake a deeper chocolate flavour and a softer crumb.

5. Bake the Cake

Divide the batter evenly between the prepared cake tins

Bake until the cakes are risen and a skewer inserted into the centre comes out with a few moist crumbs. Avoid overbaking, as this can make the cake dry.

As a guide:

• Two round cake tins: bake for about

  30–35 minutes

• One deeper cake tin: bake for about

  40–50 minutes

  , depending on the size and depth

Let the cakes cool in the tins for 10–15 minutes, then transfer them to a wire rack to cool completely before frosting.

Chocolate Buttercream Frosting

6. Beat the Butter

Place the softened unsalted butter in a large bowl and beat for 2–3 minutes, until pale, smooth, and fluffy.

This step helps create a lighter buttercream, so don’t rush it.

7. Add the Icing Sugar and Cocoa Powder

Sift the icing sugar and cocoa powder if they look lumpy.

Add them to the butter in stages, mixing slowly at first to avoid a cloud of sugar. Once incorporated, increase the speed and beat until smooth.

8. Adjust the Texture

Add the milk, 1 tablespoon at a time, until the buttercream is soft, creamy, and easy to spread.

Mix in the vanilla extract and beat again until fluffy. If the buttercream is too thick, add a little more milk. If it becomes too soft, add a spoonful of icing sugar.

Assemble the Cake

9. Level the Cakes

Once the cakes are completely cool, level the tops if needed using a sharp knife or cake leveller.

10. Frost the Cake

Place one cake layer on a serving plate or cake stand. Spread a generous layer of chocolate buttercream over the top.

Add the second cake layer, then cover the top and sides with the remaining buttercream. Smooth with a spatula or create swirls for a rustic homemade finish.

11. Slice and Enjoy

Slice and serve as it is, or decorate with chocolate shavings, sprinkles, berries, or a dusting of cocoa powder.

Tips and Tricks

✅ Cool the cake completely before frosting. If the cake is still warm, the buttercream will melt and slide off.

✅ Don’t worry if the batter looks thin. This is exactly how it should be. The extra liquid helps create a soft, moist chocolate cake.

✅ Use hot water, not boiling water. Hot water helps bring out the cocoa flavour, but it should be poured in carefully and mixed gently.

✅ Sift the cocoa powder and icing sugar. This helps prevent lumps in both the cake batter and the buttercream.

✅ Do not overbake. The cake is ready when a skewer comes out with a few moist crumbs, not completely dry.

✅ Use room-temperature ingredients where possible. Eggs, milk, and butter mix more evenly when they are not too cold.

✅ Beat the butter well before adding sugar. This makes the buttercream lighter, smoother, and easier to spread.

✅ Adjust the buttercream texture gradually. Add milk one tablespoon at a time until it reaches the perfect spreading consistency.

✅ For extra chocolate flavour, add coffee. You can replace the hot water with hot coffee. It won’t make the cake taste strongly of coffee, but it will deepen the chocolate flavour.

✅ Make it ahead. The cake layers can be baked a day in advance. Wrap them well once cooled and frost the next day.

✅ Storage tip. Keep the cake in an airtight container at room temperature for 2–3 days, or in the fridge for up to 5 days. Bring chilled slices to room temperature before serving for the best texture.