Chocolate Birthday Cake

Ingredients

• 200 g (1¾ sticks)unsalted butter
• 120 ml (½ cup)milk
• 240 g (1¾ cups)plain flour
• 1½ teaspoonsbicarbonate of soda
• 65 g (⅔ cup)cocoa powder
• 300 g (1½ cups)granulated sugar
• ¼ teaspoonsalt
• 2 largeeggs
• 160 ml (⅔ cup)sour cream
• 120 ml (½ cup)hot water or coffee (hot water mixed with 1–2 teaspoons instant coffee powder or granules)
• 200 g (7 oz)milk chocolate
• 100 g (7 tablespoons), cut into piecesunsalted butter
• 90 g (¾ cup), optionalicing sugar
• 150 ml (½ cup plus 2 tablespoons)double cream
• ⅛ teaspoonsalt
• 1 teaspoon, optionalinstant coffee powder or granules
• 200 g (7 oz), finely choppeddark or bittersweet chocolate
• 180 ml (¾ cup)double cream

Instructions

1. 1

   Prepare the tin

   Heat the oven to 180°C. Grease a 23 × 33 cm (9 × 13-inch) tin and set it aside.

2. 2

   Melt the butter

   Melt the 200 g butter, stir in the milk, then leave the mixture to cool slightly.

3. 3

   Mix the batter

   In a large bowl, combine the flour, bicarbonate of soda, cocoa powder, sugar and salt. Add the butter mixture, eggs and sour cream, mixing just until combined. Pour in the hot water or coffee and whisk until smooth.

4. 4

   Bake the cake

   Scrape the batter into the prepared tin. Bake for 30–35 minutes, until a skewer inserted into the centre comes out clean. Avoid overbaking, which can dry the cake out. Leave it to cool completely on a wire rack.

5. 5

   Make fudge frosting

   For frosting option 1, put the milk chocolate, butter, icing sugar if using, 150 ml cream, salt and optional instant coffee in a medium saucepan. Warm over low to medium heat, stirring continuously, until the chocolate and butter have melted and the mixture is lump-free. Leave it to cool in the pan for 10–15 minutes.

6. 6

   Make chocolate ganache

   For frosting option 2, put the chopped chocolate and 180 ml cream in a medium heatproof bowl. Microwave in 20–30-second bursts, stirring between each, until melted. Alternatively, set the bowl over a pan of simmering water and stir occasionally until melted.

7. 7

   Frost and chill

   Spread your chosen frosting evenly over the cooled cake and add sprinkles if desired. Refrigerate for 1 hour, until set, and keep the cake in the fridge.

8. 8

   Serve the cake

   Store the cake in an airtight container in the refrigerator for up to 5 days. Bring it to room temperature before serving for the best texture.

What is a chocolate birthday cake?

A chocolate birthday cake is a celebratory bake made to share, often finished with a rich frosting and decorations. This version is baked in a rectangular tin, making it straightforward to portion for a gathering.

The cake takes a familiar home-baking approach: cocoa gives it its chocolate flavour, while sour cream and melted butter help make the crumb tender. Choose between a milk chocolate fudge topping and a simpler dark chocolate ganache.

Nutrition and macros by portion

The nutrition label shows one serving as written: 9260 calories, 115g protein, 820g carbs, 610g fat.

Most of the carbohydrates come from the flour, sugar and chocolate, while butter, chocolate and cream provide much of the fat. Eggs, dairy and chocolate contribute some protein. The recipe lists one serving, so this estimate treats the full ingredient list as one serving; for a more balanced plate, serve a smaller slice with fresh fruit.

The ingredients that shape the crumb

Cocoa and sugar: cocoa brings a deep chocolate note, while granulated sugar sweetens the batter and helps keep the cake moist. Sifting is not specified in the method, so focus on mixing the dry ingredients evenly.

Sour cream and eggs: these enrich the batter and help it set into a soft, cohesive cake. Mix only until the ingredients come together before adding the hot liquid.

Why add hot coffee or water?

Hot liquid loosens the batter, making it easier to whisk smooth after the thicker ingredients are mixed in. The recipe allows plain hot water or coffee made with instant coffee.

Coffee adds a subtle mocha note alongside the cocoa; use hot water if you prefer the cake without that extra flavour.

How to judge when it is baked

Start checking at 30 minutes, within the recipe’s 30–35-minute baking window. A skewer inserted in the centre should come out clean.

Take care not to leave the cake in the oven longer than needed, as overbaking can make it dry. Cool it completely on a wire rack before adding frosting.

Choosing a frosting

Fudge frosting: the milk chocolate, butter and cream mixture is heated gently in a saucepan. Stir continuously and stop when it is melted and smooth; the optional icing sugar gives it a fudgier texture.

Ganache: dark or bittersweet chocolate and cream are melted together, either in short microwave bursts or over simmering water. Stir between microwave bursts to help the mixture melt evenly.

Setting and serving

Spread the chosen topping over the cooled cake, then refrigerate it for 1 hour so the frosting can set. Keep the cake chilled after that.

For the best texture, let a portion come to room temperature before serving. Sprinkles are an optional finishing touch for a birthday table.

What to serve alongside it

The cake is rich, so a modest slice pairs well with fresh berries or sliced fruit. Their freshness offers contrast without needing another elaborate dessert.

For a simple celebration spread, serve it with tea or coffee. The optional coffee in the cake or frosting also suits a coffee-based accompaniment.

Recipe notes & tips

• Use either the fudge frosting or the ganache rather than spreading both over the cake.
• Let the melted butter and milk mixture cool slightly before adding it to the eggs and sour cream.
• Whisk in the hot liquid until the batter is smooth, but avoid overmixing the earlier stage.
• Check the centre with a skewer from 30 minutes onwards.
• Cool the cake completely before frosting so the topping does not melt.
• Bring slices to room temperature before serving for a softer texture.

Variations

• Mocha cake: use coffee instead of hot water to give the cocoa a coffee note.
• Mocha frosting: add the optional instant coffee powder or granules to the fudge frosting.
• Fudgier topping: include the optional icing sugar in the milk chocolate frosting.
• Dark ganache: choose bittersweet chocolate for the ganache option.
• Birthday finish: scatter sprinkles over the frosting before chilling.

Common mistakes to avoid

• Overbaking: check from 30 minutes and remove the cake when a centre skewer comes out clean.
• Frosting a warm cake: cool it completely first so the topping stays in place.
• Heating the fudge frosting too quickly: use low to medium heat and stir continuously to prevent lumps.
• Microwaving ganache for too long: use 20–30-second bursts and stir between each one.
• Skipping the chill: refrigerate the frosted cake for 1 hour so the topping can set.

How to store

Keep the cake in an airtight container in the refrigerator for up to 5 days. Let it come to room temperature before serving; the recipe does not specify a reheating method.

Frequently asked questions