Passionfruit buttercream

PREP: 30 minutes per batch

12.5 CM (5 INCH) CAKE

60 ml (2 fl oz/¼ cup) passionfruit juice (approximately 3 passionfruit)

3 egg whites (use pasteurised)

200 g (7 oz) caster (superfine) sugar

325 g (11½ oz) unsalted butter, at room temperature

orange food colouring

1 teaspoon passionfruit seeds

18 CM (7 INCH) CAKE

100 ml (3½ fl oz) passionfruit juice (approximately 4 passionfruit)

4 egg whites (use pasteurised)

260 g (9¼ oz) caster (superfine) sugar

450 g (1 lb) unsalted butter, at room temperature

orange food colouring

2 teaspoons passionfruit seeds

23 CM (9 INCH) CAKE

160 ml (5¼ fl oz) passionfruit juice (approximately 7 passionfruit)

7 egg whites (use pasteurised)

460 g (1 lb ½ oz) caster (superfine) sugar

675 g (1 lb 8 oz) unsalted butter, at room temperature

orange food colouring

4 teaspoons passionfruit seeds

1. Put the passionfruit juice in a saucepan over high heat and bring to the boil. Turn the heat down and simmer the juice until it has reduced by half. Remove from the heat and allow to cool.
2. Fill a saucepan one-third full of water and bring it to the boil, then turn the heat down so that the water is gently simmering. Set a heatproof bowl in the top of the saucepan, making sure that the bottom of the bowl doesn’t touch the water.
3. Put the egg whites and the sugar into the bowl. Stir the mixture until all the sugar has dissolved: you should be able to rub a little of the egg white in between your thumb and fingers and not feel any grittiness from the sugar. Remove the bowl from the saucepan and transfer the egg white mixture to the bowl of a standing electric mixer (if you are using one). Using the highest setting, beat the egg whites for about 10 minutes until they are at the stiff peak stage (when you lift the beaters up a stiff peak should form; it should keep its shape and not flop over).
4. Add the butter, a small piece at a time, and beat in well. Don’t worry if at some stage the mixture starts to look curdled, keep beating and the butter will incorporate into the meringue. Once all the butter has been added, beat for a few more minutes.
5. Beat in the cooled passionfruit juice.
6. If you want to create different coloured buttercream, add the orange food colouring at this stage. You should find that the fruit juice has already given a beautiful orange tone, so one cake can be left with this natural tone. Add a little bit of the food colouring at a time until you achieve the desired shade.
7. Take a portion of each of the buttercreams and mix together with the passionfruit seeds, to use as the filling for the cake. Use 150 g (5½ oz) of buttercream for the 12.5 cm (5 inch) cake, 300 g (10½ oz) for the 18 cm (7 inch) cake and 450 g (1 lb) for the 23 cm (9 inch) cake, then reserve the remainder of the buttercream for the crumb-coat and decoration.