A friend and I made this sandcastle cake for a surprise 30th birthday party. We were both pretty impressed with how it turned out so I thought I would share how to make it. Blogging about it was a bit of an afterthought though so apologies for the lack of ‘in progress’ photos!

The good thing about this cake is that it doesn’t need to look perfect and completely symmetrical. You can use whatever size and shape cake tins you have, and your castle can be as adventurous and as detailed – or as simple – as you like.


This cake is made up of three layers. The base is a 10 inch square sponge and the middle layer is an 8 inch round sponge. The top layer was originally an 8 inch cake, but we cut around a bowl to make it smaller – you could use a smaller cake tin if you have one.

Step 1: Make the sponge cakes
The following recipe fills 2 x 8 inch round cake tins (to fill 2 x 10 inch square tins, double the recipe):

  • 225g butter
  • 225g caster sugar
  • 1 teaspoon vanilla extract
  • 4 large eggs
  • 225g self-raising flour
  • 1 teaspoon baking powder

1. Pre-heat the oven to 180C/gas mark 4 and line the bottom of the cake tins with greaseproof paper.

2. Mix the butter, sugar and vanilla extract.

3. Add the eggs one at a time, adding a bit of flour after each one to stop the mixture curdling.

4. Add the rest of the flour and the baking powder, mix well and pour into the cake tins.

5. Bake for 25 minutes in the oven (30 for the 10 inch square cake).

Alternative recipes 

For chocolate sponge:
Replace the caster sugar with soft brown sugar, reduce the flour to 200g  and add 25g of cocoa powder.

Gluten Free:
We used gluten free self-raising flour and biscuits (for the sand). The only things which weren’t gluten free were the ice cream cornets, but those were just used for decoration.

Step 2: Assembling the cake
Once cooled, sandwich the cake together with jam, put the layers on top of each other and cover with buttercream. A lot of buttercream. So much that we actually broke the hand mixer! We used 425g butter and 850g icing sugar, with a dash of vanilla essence.

Step 3: Creating the sand 
Crush approx 750g of plain biscuits using a blender. We used a mix of shortbread, digestive biscuits and ginger nuts, and also added a couple of handfuls of fine brown sugar (optional).

Take handfuls of the ‘sand’ and cover the whole cake, lightly pressing the sand into the buttercream. Sprinkle some sand around the bottom of the cake, covering the cake board. This can make quite a lot of mess so its best to add the sand to the cake board when you are ready to display the cake.


Step 4: Making the turrets
Put the remaining sand mixture into a shallow dish or on a plate. In a separate bowl, mix some icing sugar with a small amount a water to make royal icing. Take an ice cream cornet (the ones with the flat bottoms work really well) and cover in royal icing, then roll in the sand mixture. Place the cornets upside down on the cake.

Step 5: The finishing touches
We added little flags (make your own using triangles of coloured paper and cocktail sticks), white chocolate sea shells and a mini bucket and spade.

You could add little fish, bath toys, a mermaid, diggers – anything you like!

Shopping List 

  • 1.5kg butter
  • 1kg caster sugar
  • 1kg self-raising flour
  • 1.5kg icing sugar
  • 16 eggs
  • Vanilla extract
  • Baking powder
  • Jam
  • 750g biscuits
  • Ice cream cornets
  • Decorations
  • Cake Board
  • Optional:
    Soft brown sugar
    Cocoa powder


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