zoom Martha Collison's rhubarb & custard piñata cake

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    Martha Collison's rhubarb & custard piñata cake

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    Martha Collison's rhubarb & custard piñata cake

    A hidden centre of rhubarb and custard sweets inside this impressive-looking cake is the perfect thing to surprise your loved one

    • Preparation time: 40 minutes + cooling
    • Cooking time: 25 minutes to 30 minutes
    • Total time: 1 hour 5 minutes to 1 hour 10 minutes + cooling

    Serves: 12 - 14


    250g butter, softened, plus extra for greasing
    300g caster sugar
    4 medium Waitrose British Blacktail Eggs, at room temperature
    300g plain flour
    3½ tsp baking powder
    50g instant custard powder
    125ml milk

    250g unsalted butter, softened
    500g icing sugar
    2 tbsp instant custard powder
    2 tbsp milk
    Pink and yellow food colouring

    4 tbsp Waitrose Rhubarb & Ginger Preserve
    2 x 225g packets Waitrose Rhubarb & Custard Sweets


    1. Preheat the oven to 180°C, gas mark 4, and grease and line the bases of three 18cm cake tins with baking parchment.

    2. Using a hand-held electric whisk or a stand mixer, cream together the butter and sugar until really light and fluffy. Add the eggs one at a time, whisking after each addition.

    3. In a small bowl, combine the flour, baking powder and custard powder. Add these dry ingredients into the egg mixture a few tablespoons at a time, and continue to mix until a smooth batter forms. Pour in the milk and mix again.

    4. Divide the mixture between the three tins, and use a spatula to smooth over the tops. Bake for 25-30 minutes, or until golden and well risen. A skewer inserted into the centre should come out clean. Allow to cool briefly in the tins before turning out onto a wire rack to cool completely.

    5. For the buttercream, beat the softened butter and icing sugar using a hand-held electric whisk or stand mixer until it forms a smooth paste. Add the custard powder and the milk, then beat on a high speed for 3-4 minutes until light, fluffy and pale in colour. Spoon ¼ of the buttercream into a separate bowl and add enough pink food colouring to match the pink section of one of the rhubarb and custard sweets. Add yellow food colouring to the remaining buttercream to match the yellow section of the sweet.

    6. To assemble the cake, stack the bottom 2 layers of sponge on top of each other, and use a circular 10cm cutter to remove the middle. Press through both layers at once to make sure the holes line up.

    7. Place one of the cut rings on a cake stand and cover the top with a layer of yellow buttercream using a palette knife. Spread a generous amount of the rhubarb jam on top of the icing. Try not to get icing or jam too close to the middle because moisture on the sweets will cause them to become sticky.

    8. Put the second cut ring on top of the first and fill the cavity with rhubarb and custard sweets, reserving 2-3 for decorating. Make sure the hole is filled to the same level as the sponge or the top sponge will cave in. Apply buttercream and jam to the top and place on the final sponge. Thinly cover the whole cake with a little more of the yellow buttercream to trap any crumbs, then chill for at least 30 minutes.

    9. Use a palette knife to apply some more of the yellow icing to the top of the cake and blend it over the edges to create a smooth top. Take both colours of icing and apply random splodges to the sides of the cake, swirling them around with the tip of a palette knife. Keep adding each colour until you’re happy with the finish – it should be like choppy water. Crush the reserved sweets and sprinkle around the top edge of the cake. It is best to eat the finished product on the day it is assembled or the sweets will stick together inside. 

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