The first time I made this, I was mid-mix when I realised my sugar thermometer had vanished into the drawer of doom. Cue frantic Googling and stumbling upon the “instant” version of American frosting. Honestly? It saved the bake and my nerves.
This cake? It’s everything a proper Devil’s Food Cake should be: a deep, dark cocoa flavour, a soft, tender crumb, and that perfect balance of bitter and sweet. And the frosting? Well, it turns a delicious cake into something truly irresistible. It sets into a glossy shell with a crackly top, while the inside stays light and marshmallowy.
Whether you stick to the sugar syrup method or take the shortcut, this one’s a keeper. It has an old-school bakery vibe but feels modern enough for any celebration.
Why This Recipe Works
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Cocoa + Bicarb = Chocolate Depth – It gives the cake a rich, chocolate punch without being overly sweet.
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Boiling Water Blooms the Cocoa – This intensifies the flavour. Don’t skip this step!
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Frosting Sets Like a Dream – A crisp top with a soft, marshmallow centre.
Ingredients & Why They Matter
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50g Cocoa Powder – Choose a high-quality, unsweetened cocoa for the richest flavour.
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225ml Boiling Water – Helps the cocoa bloom and enhances the chocolate taste.
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100g Soft Margarine – Keeps the cake moist and tender.
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275g Caster Sugar – Adds sweetness and contributes to the cake’s structure.
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Bicarb & Baking Powder – Key for a light rise and tender crumb.
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175g Plain Flour – Helps keep the cake fine-crumbed and tender.
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American Frosting (Egg Whites, Sugar, Water) – A no-butter frosting that’s light and fluffy.
Customizations You Can Try
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Frosting Alternative – If you’re not up for boiling sugar, go with chocolate ganache or whipped cream instead.
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Boozy Twist – Add a tablespoon of coffee liqueur to the cake batter to intensify the chocolate.
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Cupcake Version – Bake at the same temperature for 18–20 minutes.
Mistakes I’ve Made (And How to Avoid Them)
| What Went Wrong | Why It Happens | How to Fix It |
|---|---|---|
| Cake too dry | Overbaked or cocoa not bloomed | Check at 30 mins and make sure you bloom the cocoa. |
| Frosting too runny | Didn’t whip it enough | Whisk until the frosting looks matte and thick. |
| Frosting set too fast | Waited too long to use it | Work quickly once the frosting is ready. |
How to Make Mary Berry’s Devil’s Food Cake
1. Preheat & Prep
Preheat your oven to 180°C / 350°F / Gas 4. Grease and line two 20cm sandwich tins with baking paper.
2. Make Cocoa Mix
Whisk 50g cocoa powder into 225ml boiling water until smooth. Set aside to cool slightly.
3. Cream Butter & Sugar
Beat 100g margarine and 275g caster sugar together until pale and fluffy. Lightly whisk 2 eggs, then gradually add them to the mix, beating well.
4. Fold in Dry & Wet Ingredients
Sift 175g plain flour, ¼ tsp baking powder, and 1 tsp bicarb. Fold into the butter mixture, alternating with the cocoa mixture until well combined.
5. Bake
Divide the batter between the two tins. Bake for 30–35 minutes, or until a skewer comes out clean. Cool in the tins for 5 minutes, then transfer to a wire rack to cool completely.
6. Make American Frosting
In a saucepan, heat 450g sugar with 135ml water until it reaches 115°C (soft ball stage). Meanwhile, whisk 2 egg whites to stiff peaks. Slowly pour the hot syrup into the egg whites while whisking continuously. Continue whisking until thick, glossy, and slightly matte around the edges.
7. Assemble the Cake
Spread a small amount of frosting on one cake layer. Place the second cake layer on top, then spread the remaining frosting over the top and sides, creating soft peaks with a palette knife. Let it set.
Quick Frosting (No Thermometer)
If you don’t have a thermometer, whisk 2 egg whites with ½ tsp cream of tartar to soft peaks. Gradually add 200g icing sugar and 1 tsp vanilla extract. Whisk until thick and glossy, then use immediately.
Kitchen Tips
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Work Quickly with the Frosting – It sets fast, so have your palette knife ready.
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Watch the Sugar Syrup – If it goes over 115°C, it will start to crystallise. Keep an eye on it.
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Cool the Cakes Before Frosting – Otherwise, the frosting will melt and slide off.
Storage & Serving
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Room Temp: Keeps for up to 3 days in an airtight tin.
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Fridge: Can be refrigerated for up to 5 days, but bring it to room temperature before serving.
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Freezer: Freeze the unfrosted layers wrapped tightly for up to 3 months. Thaw before frosting.
Frequently Asked Questions
Q: Can I use butter instead of margarine?
A: Absolutely—just make sure the butter is softened to cream smoothly.
Q: Do I need a sugar thermometer?
A: It helps, but if you don’t have one, use the instant frosting method. It’s easy and still gives you that fluffy, meringue-like texture.
Q: Can I make this gluten-free?
A: Yes, simply swap for a 1:1 gluten-free flour blend and add ½ tsp xanthan gum if needed.
More Recipes to Try:
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Mary Berry Chocolate Chip Cheesecake
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Mary Berry Celebration Chocolate Mousse Cake
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Mary Berry Malted Chocolate Cake
