Two favourites collide in this mash-up of birthday cake and fairy bread. Party hats mandatory. Begin this recipe a day ahead to make the rainbow sprinkles.
- 375 gm (2½ cups) plain flour
- 75 gm (½ cup) cornflour, plus extra for dusting
- 450 gm vanilla sugar (see note)
- 2½ tsp baking powder
- 165 gm butter, coarsely chopped
- 195 gm eggwhites, at room temperature (about 6 eggs)
- 270 ml milk, at room temperature
- 1½ tbsp vegetable oil
- 75 gm white chocolate
- 3 eggwhites
- 110 gm (½ cup) caster sugar
- Scraped seeds of ½ vanilla bean
- 90 gm butter, softened
- 150 gm fondant
- Red, yellow, green and blue food colouring
- 1For sprinkles, divide fondant into 4 pieces. Starting with one piece, knead on a surface lightly dusted with cornflour until smooth and pliable, then add 2-3 drops of food colouring, kneading until smooth and coloured evenly. Repeat with remaining fondant and colours. Roll out each piece to 2.5mm thick, brushing off excess flour. Punch out discs with a plain 7mm piping-bag nozzle, transfer to a tray lined with baking paper and dry at room temperature overnight. Store in an airtight container until required.
- 2Preheat oven to 160°C. Grease two 20cm square cake tins and line them with baking paper. Combine flour, cornflour, vanilla sugar and baking powder in an electric mixer fitted with the paddle attachment. Add butter and beat to coarse crumbs. Add eggwhite and beat until a paste forms, then add milk and oil and beat until smooth (5 minutes). Divide among tins and bake until golden, risen and a skewer inserted withdraws clean or with only dry crumbs (30-35 minutes). Cool briefly in tins, then turn out onto a wire rack lined with baking paper to cool completely.
- 3For buttercream, melt chocolate in a bowl over a saucepan of simmering water (don't let bowl touch water). Set aside. Combine eggwhite and sugar in a separate bowl and place over simmering water. Whisk until hot to touch (or 55°C on a thermometer), then transfer to an electric mixer and whisk on high speed until thick, glossy and cooled to room temperature. Beat in chocolate. vanilla and butter until smooth
- 4Spread a third of the buttercream over one cake, top with other cake and spread with remaining buttercream. Scatter with sprinkles and cut into triangles to serve. Note For vanilla sugar, store used scraped vanilla beans in caster sugar, or combine scraped seeds of ½ vanilla bean with the caster sugar.