Chocolate volcano cake with sparkler on tray

Volcano cake

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(3 ratings)

Prep: 1 hr, 15 mins Cook: 45 mins


Serves 12 - 16

Make our spectacular exploding volcano cake complete with eruption effect for a showstopping children's treat. Decorate with chocolate and sweets

Nutrition and extra info

  • Vegetarian

Nutrition: per serving (16)

  • kcal717
  • fat38g
  • saturates20g
  • carbs84g
  • sugars67g
  • fibre3g
  • protein9g
  • salt0.84g
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  • 300g very soft butter



    Butter is a dairy product made from separating whole milk or cream into fat and…

  • 300g caster sugar
  • 6 large eggs
  • 300g self-raising flour
  • 2 tbsp milk



    One of the most widely used ingredients, milk is often referred to as a 'complete' food…

  • red paste food colouring
  • 500g marzipan
    Marzipan cake



    One of mankind’s oldest sources of sweet pleasure, marzipan needs to contain only ground…

  • icing sugar, to dust for rolling out marzipan
  • 200g dark chocolate
    Dark chocolate soup pots with double cream in spoons

    Dark chocolate

    dahk chok-o-let

    Dark chocolate means the shiny, dark-reddish brown treat produced from the cacao bean, theobroma…

  • about 250g assorted chocolate decorations (Maltesers, Crunchie bites, chocolate covered raisins)
  • 400g red buttercream
  • sparklers to decorate

For the explosion

  • 1 pack of Mentos
  • big bottle of diet coke
  • a dash of red food colouring
  • A small Evian bottle (empty)


  1. Preheat the oven to 180C/160C fan/gas 4. Grease and line an 18cm round cake tin and an 800–900ml oven proof (Pyrex) bowl. 

  2. Put the butter, sugar, eggs, flour and milk into a large bowl and beat well until light and creamy.

  3. Place about 450g cake mix in the cake tin in heaped spoonfuls, then take approximately 450g cake mix and stain it a bright red in a mixing bowl. Place 175g red cake mix dotted around the cake tin amongst the white batter and mix through with the end of a spoon to marble. Place the remaining white and red batter in the bowl and swirl to marble it.

  4. Bake in the oven for 30-40 mins for the cake tin and 40-45 mins for bowl. The mixture is cooked when firm to the touch and when a skewer inserted into the centre comes out clean.

  5. When the cakes are cold trim off any peaks that have formed. Use a knife to cut a hole in the cake tin sponge to fit the bottle. For the bowl shape, slice this in half horizontally, then cut the hole out in both pieces to fit the bottle. We used a small Evian 330ml bottle, but you can use any bottle as long as it is small. 

  6. Place the round cake on a 7” round cake card and then on a further large cake board. Spread some buttercream on the top of the cake, using a little more to stick the sponge off-cuts around the cake against the base. Now add the larger part from the bowl sponge and sandwich onto the buttercream. Spread over some more buttercream. Add the hump part of the bowl cake, rounded side up, on top.

  7. Using some of the sponge off-cuts, build up the cake to meet the top of the bottle, using buttercream to stick it all together and now go over the whole shape with the rest of the buttercream to seal and make sticky for the marzipan.

  8. Roll out the marzipan to a large circle to cover the cake's top and sides – it can be quite a rough shape. Lift it onto the cake and drape in a random fashion in the nooks and crannies to make a volcano shape.

  9. Melt the chocolate in a microwave or in a bowl over a pan of hot water. Using a pastry brush, paint the volcano with chocolate. Attach chunks of chocolate and sweets to make the rocky effect. Drizzle any remaining chocolate over the volcano.

  10. Now it's time for the explosion. In a jug, add 330ml of diet coke and mix with a dash of red food colouring. Very carefully, with a funnel if necessary, pour the coke into the hidden bottle. Get five mentos ready and roll up some paper to make a little tube so you can drop them all in at once. When you are ready, pop the mentos into the bottle and watch the foamy lave bubble up and pour over the cake. For extra effect use birthday candles, cake sparklers, or cake fountains.

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Comments, questions and tips

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1st Jul, 2018
The idea for this cake is brilliant, but unfortunately the Evian bottle suggested in the recipe doesn't give an explosive effect, more of a dribble over the sides. We tried this with several different types of small bottles and the main problem was that when the coke was poured into the bottle it lost some of its fizz, also there wasn't enough coke to provide a spectacular explosion. In the end we made a bigger hole in the middle of the cake, enough to slot in the top half of a 1.25L coke bottle. We also made a corresponding hole in a cake board and sat the cake on it. We then put this between two tables with the coke bottle propped on a stool underneath. A table cloth covered the table so the bottom half of the coke bottle couldn't be seen. With this volume of coke and a full pack of Mentos, we got a pretty awesome explosion. Although we did have to ask the children to stand back a bit! I'd recommend experimenting with the explosive effect in advance so you get what you're hoping for.
11th Oct, 2019
Is the cake actually edible after the explosion? Does it go soggy? And does it taste strongly of coke and mint?
Liz midwinter's picture
Liz midwinter
9th Sep, 2018
Hi, this cake looks amazing. I was just wondering if you could substitute the marzipan for rolled fondant icing? Many thanks.
goodfoodteam's picture
11th Sep, 2018
Thanks for your question. We haven't tested this but would suggest chocolate fondant icing as the best alternative.
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