This Nigella-inspired chocolate sheet cake is soft, rich, and topped with a smooth cocoa frosting. It’s easy to make and perfect for any occasion, whether you want big squares, snack bars, or bite-sized treats!
Ingredients Needed:
For the Cake:
- 125 milliliters of full-fat milk or semi-skimmed / 2% milk
- 2 teaspoons white wine vinegar or cider vinegar
- 200 grams of soft unsalted butter
- 20 grams of best-quality cocoa powder
- 200 grams caster sugar
- 1 teaspoon bicarbonate of soda
- 1 pinch of salt
- 300 grams of plain flour
- 2 large eggs
- 1 teaspoon vanilla extract
For the Icing/Frosting:
- 50 grams of soft unsalted butter
- 3 tablespoons full-fat milk or semi-skimmed / 2% milk
- 2 tablespoons best-quality cocoa powder
- 150 grams of icing sugar (sieved)
- 1 teaspoon vanilla extract
To Decorate:
- Sprinkles of your choice
How To Make Chocolate Sheet Cake?
- Preheat the oven: Set it to 180ºC and grease and line a 33cm x 23cm roasting tin or 30cm x 20cm tin.
- Prepare the buttermilk: Mix the milk and vinegar in a jug and let it sit while you get everything else ready.
- Melt the butter and cocoa: In a large saucepan, add 250ml water, butter, and cocoa powder. Heat on medium, stirring until the butter melts. Remove from heat.
- Mix the dry ingredients: In a bowl, whisk together the sugar, bicarbonate of soda, salt, and flour.
- Prepare the wet ingredients: Add the eggs and vanilla to the buttermilk and whisk well.
- Combine everything: Add the dry ingredients to the saucepan with the melted butter mixture. Stir, then pour in the buttermilk mixture and mix until smooth.
- Bake the cake: Pour the batter into the prepared tin and bake for about 20 minutes, or until a tester comes out clean. Place the tin on a wire rack.
- Make the icing: While the cake is baking, melt the butter, milk, and cocoa in a saucepan over low heat, stirring continuously. Do not let it boil.
- Finish the icing: Remove from heat and whisk in the icing sugar and vanilla until smooth and glossy.
- Frost the cake: Pour the icing over the hot cake immediately and spread evenly with a spatula.
- Add decorations: Sprinkle your favorite toppings while the icing is still wet.

Recipe Tips:
- Use room temperature ingredients: Cold butter or eggs can affect the texture of the cake. Let them sit at room temperature before using for a smooth batter.
- Sift the dry ingredients: Sifting the flour, cocoa powder, and icing sugar removes lumps and makes the cake and frosting smooth and even.
- Don’t overmix the batter: Stir just until everything is combined. Overmixing can make the cake dense instead of light and soft.
- Pour the icing while the cake is hot: The frosting sets quickly, so make sure to spread it over the cake as soon as it comes out of the oven for the best finish.
- Check the cake early: Every oven is different, so start checking at 18 minutes. The cake is done when a toothpick comes out with a few moist crumbs but no wet batter.
How To Store Leftovers?
- Refrigerate: Let the chocolate sheet cake cool completely. Then, store it in an airtight container in the fridge for up to 5 days.
- Freeze: Once the cake is cool, cut it into pieces and wrap each piece well. Store them in a freezer-safe container and freeze for up to 3 months.
Nutrition Facts:
- Calories: 320 kcal
- Total Fat: 14g
- Saturated Fat: 8g
- Cholesterol: 60mg
- Sodium: 180mg
- Potassium: 120mg
- Total Carbohydrate: 45g
- Dietary Fiber: 2g
- Sugars: 30g
- Protein: 4g
Try More Nigella Lawson Recipes:
- Nigella Chocolate Cherry Cake
- Nigella Chocolate Chestnut Refrigerator Cake
- Nigella Chocolate Olive Oil Cake

Nigella Chocolate Sheet Cake
Description
This Nigella-inspired chocolate sheet cake is soft, rich, and topped with a smooth cocoa frosting. It’s easy to make and perfect for any occasion, whether you want big squares, snack bars, or bite-sized treats!
Ingredients
For the Cake:
For the Icing/Frosting:
To Decorate:
Instructions
- Preheat the oven: Set it to 180ºC and grease and line a 33cm x 23cm roasting tin or 30cm x 20cm tin.
- Prepare the buttermilk: Mix the milk and vinegar in a jug and let it sit while you get everything else ready.
- Melt the butter and cocoa: In a large saucepan, add 250ml water, butter, and cocoa powder. Heat on medium, stirring until the butter melts. Remove from heat.
- Mix the dry ingredients: In a bowl, whisk together the sugar, bicarbonate of soda, salt, and flour.
- Prepare the wet ingredients: Add the eggs and vanilla to the buttermilk and whisk well.
- Combine everything: Add the dry ingredients to the saucepan with the melted butter mixture. Stir, then pour in the buttermilk mixture and mix until smooth.
- Bake the cake: Pour the batter into the prepared tin and bake for about 20 minutes, or until a tester comes out clean. Place the tin on a wire rack.
- Make the icing: While the cake is baking, melt the butter, milk, and cocoa in a saucepan over low heat, stirring continuously. Do not let it boil.
- Finish the icing: Remove from heat and whisk in the icing sugar and vanilla until smooth and glossy.
- Frost the cake: Pour the icing over the hot cake immediately and spread evenly with a spatula.
- Add decorations: Sprinkle your favorite toppings while the icing is still wet.
Notes
- Use room temperature ingredients: Cold butter or eggs can affect the texture of the cake. Let them sit at room temperature before using for a smooth batter.
- Sift the dry ingredients: Sifting the flour, cocoa powder, and icing sugar removes lumps and makes the cake and frosting smooth and even.
- Don’t overmix the batter: Stir just until everything is combined. Overmixing can make the cake dense instead of light and soft.
- Pour the icing while the cake is hot: The frosting sets quickly, so make sure to spread it over the cake as soon as it comes out of the oven for the best finish.
- Check the cake early: Every oven is different, so start checking at 18 minutes. The cake is done when a toothpick comes out with a few moist crumbs but no wet batter.
Nigella Chocolate Sheet Cake