This moist, fudgy Mary Berry Chocolate Tray Bake is made with a clever cocoa paste method and topped with a glossy chocolate icing, ready in under an hour. The most satisfying part is pouring the warm, silky icing over the sponge and watching it set into a perfect, sliceable layer. I bake this whenever I need a reliable crowd-pleaser that transports easily and tastes incredible.

Why This Classic Works

I used to struggle with dry chocolate cakes until I tried Mary Berry’s method of mixing cocoa powder with boiling water first. This simple step blooms the cocoa, releasing a deeper flavour and creating a paste that keeps the sponge incredibly moist for days. It transforms a standard batter into something far more indulgent without any extra effort.

The other secret is using baking spread instead of butter for the sponge, which Mary herself often recommends for an aerated, lighter crumb. I learned the hard way that using block butter can sometimes make the sponge too dense if not softened perfectly, whereas baking spread guarantees a fluffy rise every time.

Mary Berry Chocolate Tray Bake Ingredients

For the Sponge:
50g cocoa powder
4 tbsp boiling water
225g baking spread (or very soft butter)
225g caster sugar
275g self-raising flour
2 tsp baking powder
4 large eggs
4 tbsp milk
For the Chocolate Icing:
50g butter
25g cocoa powder
3 tbsp milk
225g icing sugar, sifted
Optional: White or milk chocolate chips for decoration

How To Make Mary Berry Chocolate Tray Bake

Prepare the Paste: Preheat your oven to 180°C (160°C Fan/Gas 4) and grease and line a 30 x 23cm (12 x 9in) traybake tin with baking parchment. In a large mixing bowl, measure the cocoa powder and pour over the boiling water. Mix well until you have a smooth, thick chocolate paste.
Mix the Batter: Add the baking spread, caster sugar, self-raising flour, baking powder, eggs, and milk directly into the bowl with the cocoa paste. Using an electric hand whisk, beat everything together for about 2 minutes until the mixture is smooth and lighter in colour.
Bake the Sponge: Scrape the batter into your prepared tin and level the surface with a spatula. Bake for 35 to 40 minutes. The cake is done when it has shrunk slightly from the sides of the tin and springs back when pressed gently in the centre. Leave to cool in the tin.
Make the Icing: Melt the butter in a small saucepan over low heat. Whisk in the cocoa powder and milk until combined. Remove from the heat and gradually stir in the sifted icing sugar until you have a glossy, spreadable consistency.
Assemble: Pour the warm icing over the cooled cake (still in the tin) and spread it out evenly. Sprinkle with chocolate chips if using. Allow the icing to set completely before lifting the cake out of the tin and cutting it into squares.

Recipe Tips

Don’t skip the sifting: Always sift the cocoa powder and icing sugar for the topping. Tiny lumps of cocoa are notoriously hard to whisk out once liquid is added, and they will spoil the smooth finish of your icing.
The tin size matters: This recipe is specifically designed for a 30 x 23cm tray. If you use a smaller tin, the cake will be deeper and take longer to cook; a larger tin will result in a dry, flat pancake.
Cool completely: Resist the urge to ice the cake while it is hot. If the sponge is warm, the icing will run off the edges or soak into the crumb rather than sitting as a distinct, glossy layer on top.

What To Serve With Mary Berry Chocolate Tray Bake

This cake is robust enough to be eaten by hand, making it perfect for picnics or lunchboxes alongside a cup of tea. For a more formal dessert, serve a square with a dollop of clotted cream and fresh raspberries to cut through the rich sweetness.

How To Store

Store the cut squares in an airtight container at room temperature for up to 3 days. If you want to get ahead, the un-iced sponge freezes beautifully for up to a month; just defrost it fully before making and applying the fresh icing.

FAQs

Can I use butter instead of baking spread? Yes, but ensure it is incredibly soft before mixing. Baking spread is generally preferred for this all-in-one method as it blends easier and creates a lighter texture.
Why is my icing too stiff? If the icing is too thick to spread, add another teaspoon of warm milk. It should be thick enough to hold its shape but loose enough to smooth out easily.
Can I double the recipe? This recipe fills a standard large roasting tin size perfectly. If you need more, it is better to bake two separate trays rather than trying to bake a double depth cake, which may cook unevenly.

Nutrition

Calories: 285 kcal
Total Fat: 14g
Saturated Fat: 5g
Cholesterol: 65mg
Sodium: 180mg
Total Carbohydrate: 38g
Protein: 4g

Try More Recipes:

Mary Berry Chocolate Mousse Cake Recipe
Mary Berry Sponge Cake Recipe
Mary Berry Millionaire Shortbread Recipe