For the cake
- 375g/13oz butter or margarine, softened at room temperature
- 375g/13oz unrefined caster sugar
- 6 large free-range eggs
- 2 tsp vanilla extract
- 375g/13oz self-raising flour
- 2-3 tbsp milk
- few drops of blue food colouring
- few drops of red food colouring
For the Italian meringue buttercream
- 300g/10oz caster sugar
- 5 large free-range egg whites
- 500g/1lb unsalted butter, softened and cut into squares
- pinch of salt
- few drops of vanilla extract
- 6 tbsp raspberry jam
For the sponge layers, preheat the oven to 180C/160C Fan/Gas 4. Grease and line the base of three 18cm/7in cake tins with baking paper.
Cream the butter and sugar together in a bowl until pale and fluffy. Beat in the eggs, a little at a time, and stir in the vanilla extract. Fold in the flour using a large metal spoon, adding a little extra milk if necessary.
Divide the mixture equally into three mixing bowls. Add a few drops of blue colouring into one bowl and mix gently to get an even colour. Add red food coluring to the other bowl and again mix for an even colour. Leave the third mix plain.
Spoon the cake mixtures into the three cake tins and gently spread out with a spatula. Bake for 20-25 minutes, or until golden-brown on top and a skewer inserted into the middle comes out clean.
Remove from the oven and set aside for five minutes, then remove from the tin and peel off the paper. Place onto a wire rack to cool completely.
For the frosting, fill a large bowl with cold water. Pour 100ml/3½fl oz water into a pan and add 250g/9oz caster sugar. Heat gently and stir until the sugar dissolves, then bring the mixture to the boil. Use a damp pastry brush to wash down any sugar crystals on the side of the pan. Boil the mixture rapidly, without stirring it, until it reaches 121C/250F (use a kitchen thermometer for this).
Preferably using a freestanding mixer, whisk the egg whites until stiff. Start this when the sugar temperature of the syrup gets to about 100C. Gradually whisk in the remaining caster sugar.
As soon as the syrup reaches 121C/250F, plunge the base of the pan into the bowl of cold water, to prevent the syrup from getting any hotter. Only leave the pan in the water for a few seconds or the syrup will get too thick.
Switch the mixer on full speed and gradually pour in the syrup in a thin stream into the middle of the bowl, trying not to get any syrup onto the sides of the bowl or the whisk, as it will set there and won’t get mixed in properly. Continue whisking the mixture for about 8-10 minutes until the bowl feels just lukewarm. If the syrup starts to become too thick to pour, return the pan to the hob very briefly.
Gradually whisk in the butter. Then add the salt and vanilla extract. The meringue will collapse a little, and the mixture may look like it’s curdled, but keep whisking it until it forms a smooth fluffy buttercream.
Spread the jam over two of the cake layers and top with a layer of frosting. Sandwich the cakes together. Chill in the fridge for 15 minutes. Remove from the fridge and gently cover the whole of the cake with the frosting. Sprinkle with decorating sprinkles if desired.
To make the bunting decoration, take two lengths so doweling and cover with a spiral of coloured string. Tie a length of string across both doweling rods. Cut 5cm/2in lengths of ribbon or diamond-shape bits of fabric. Fold the bunting ‘flags’ over the string and glue to secure. Gently ease the doweling into the cake and you have a lovely sweep of bunting.