Mary Berry Confetti Traybake

This cake took me right back to the village fêtes I went to as a kid—plastic tablecloths, lemon barley water, and trays of colourful bakes disappearing before you got to the front of the queue.

The first time I tried this, I made two classic mistakes: I softened the margarine too much, and I skimped on the beating time. The result? A dense, slightly sunken traybake that tasted okay… but definitely didn’t have that fluffy, springy lift Mary’s is known for.

Next go, I followed her advice to the letter—chilled margarine, all-in-one method, full five-minute beat—and it was a game-changer. Soft, golden sponge, bright white icing, and cheerful sprinkles that made it feel like a celebration in a tin.

Let me show you how to nail it—no sinkage, no stress.

WHY THIS ONE WORKS SO WELL

The all-in-one method here is classic Mary Berry: simple, fast, and reliable—if you do it right. The chilled margarine might sound odd, but it makes the batter whip up light and fluffy without melting into the mix.

And the icing? Boiling water makes it smooth without needing butter or cream cheese. It sets quickly and gives that nostalgic, crisp-on-top finish we all secretly love.

Most traybakes go soft or sticky after a day—but this one holds its texture beautifully for a few days, even with the icing on.

INGREDIENTS + WHY THEY MATTER

• Chilled Margarine (225g) – Don’t use butter here. Proper block margarine from the fridge gives a fluffier sponge. Soft spread just won’t cut it.
• Superfine Sugar (225g) – Dissolves quickly and helps with the cake’s light texture. Regular sugar works in a pinch but needs longer mixing.
• Self-Raising Flour (275g) – Saves time and gives a guaranteed lift.
• Baking Powder (1 tsp) – Even with self-raising flour, this gives extra insurance for a good rise.
• Eggs (4 large) – Room temp is best—they mix better and help hold air in the batter.
• Milk (4 tbsp) – Loosens the mix slightly for better spread in the tray.
• Vanilla Extract (1 tsp) – Adds warmth and sweetness—essential with plain sponge.

For the Icing:

• Confectioners’ Sugar (300g) – Makes a smooth, quick-setting icing.
• Boiling Water (3 tbsp) – Just enough to melt the sugar and create a spreadable glaze.
• Coloured Sprinkles (2 tbsp) – Optional, but let’s be honest—half the joy is in the confetti look.

MAKING IT YOURS (WITHOUT RUINING IT)

• Want butter instead of margarine? You can use softened butter, but the texture will be a bit denser and more buttery. Still tasty, but not as fluffy.
• Going gluten-free? I tested this with Doves Farm GF self-raising—it worked, but needed an extra tablespoon of milk to loosen the batter.
• No sprinkles? Try flaked almonds or freeze-dried raspberries for a grown-up twist.
• Lemon version? Swap the vanilla for zest and juice of 1 lemon. Gorgeous.

MISTAKES I’VE MADE (AND HOW TO AVOID THEM)

WHAT WENT WRONG	WHY IT HAPPENS	HOW TO FIX IT
Cake was too dense	Margarine too soft	Use it straight from the fridge
Icing melted	Cake was still warm	Wait until fully cooled before icing
Cake cracked on top	Oven too hot or batter too stiff	Stick to the milk and smooth the top well
Icing too runny	Added too much water	Start with 2 tbsp and add slowly

HOW TO MAKE MARY BERRY’S CONFETTI TRAYBAKE

1. Preheat your oven to 180°C (160°C fan) / 350°F. Grease and line a 12×9-inch (30×23cm) traybake tin with baking paper.
2. Make the batter: In a large bowl, add the chilled margarine, sugar, self-raising flour, baking powder, eggs, milk, and vanilla extract. Use an electric mixer and beat everything together for a good 3–5 minutes until the batter is smooth and pale.
3. Bake: Pour the mixture into the tin and smooth out the top. Bake for 30–35 minutes, or until golden, slightly pulling from the sides, and springy in the middle.
4. Cool: Leave it to cool completely in the tin—no shortcuts. I once iced it early and everything slid off.
5. Ice it: Mix the confectioners’ sugar with 3 tablespoons of boiling water. Stir until smooth and pourable (but not too thin). Spread evenly over the cooled cake.
6. Decorate: While the icing is still wet, scatter on your sprinkles. Let it set before slicing into 20 squares.

TIPS FROM MY KITCHEN

• I beat the batter for a full 5 minutes—it really does make it fluffier.
• Use the back of a warm spoon to smooth the icing—it spreads cleaner.
• I keep the sprinkles in the freezer so they don’t bleed into the icing too quickly.
• If the corners bake faster, cover loosely with foil for the last 5 minutes.

STORAGE + SERVING

• Fridge: Not needed—just keep in an airtight container at room temp for up to 5 days.
• Freezer: Freeze squares in layers with baking paper in between. They defrost beautifully in a lunchbox or at room temp in under an hour.
• Serve with: A mug of tea, obviously. But also try with whipped cream or a scoop of ice cream if you’re turning it into dessert.

FREQUENTLY ASKED QUESTIONS

Q: Can I use butter instead of margarine?
A: You can, but the texture will be a little heavier. Margarine gives a lighter, fluffier sponge.

Q: My icing is too runny—what do I do?
A: Add a bit more icing sugar and stir well. It should be spreadable, not pourable.

Q: Can I halve the recipe?
A: Yes—use a smaller tin (around 8-inch square) and check it 5 minutes early.

Q: Why did my cake sink in the middle?
A: Usually underbaking or not mixing enough. Beat the batter longer and test for doneness in the centre before pulling it out.

Q: Can I make this ahead for a party?
A: Definitely. It actually improves overnight—just keep it in a container and add sprinkles the day before if you want them to stay crisp.

Try More Recipes:

• Mary Berry Iced Chocolate Traybake With Fudge Icing
• Mary Berry Gingerbread Traybake
• Mary Berry Dorset Apple Traybake