Put the seeded pulp of 5 of the passionfruit into the processor and blitz just to loosen the seeds. Strain into a jug or bowl.
Beat the egg, egg yolk and sugar together.
Melt the butter over a low heat in a heavy-based pan, and when melted stir in the sugar-egg mixture and the passion fruit juice, and keep cooking gently, stirring constantly, until thickened.
Off the heat, whisk in the pulp - seeds and all - of the remaining passionfruit, let cool slightly, then pour into a jar. Keep in the fridge
Make the ice cream
Whip the cream until soft peak stage. Add the condensed milk and whip until smooth and fluffy then stir in the passion fruit puree, zest and salt.
Make the meringue topping
in a small saucepan set over high heat, stir together 300g of the caster sugar, cream of tartar and water. Bring to a boil and without stirring, bring the mixture to 120 C on a sugar thermometer.
Meanwhile, place the egg whites in the bowl of a stand mixer fitted with the whisk attachment.
Meanwhile, place the egg whites in the bowl of a stand mixer fitted with the whisk attachment. Beat until medium peaks form then gradually add in remaining 100g caster sugar. Once combined, very carefully pour the hot sugar syrup into the mixture, making sure not to pour the syrup over the whisk. Whisk for 5 to 10 minutes until the bowl of the mixer has cooled to the touch and the meringue is thick and glossy then add the vanilla and whisk for a further minute.
Place the meringue into a piping bag fitted with a large star nozzle and remove the bombe from the freezer. Unmould and set on your serving plate then pipe circles all over the bombe. When the bombe is covered in meringue, use your blow torch to toast the meringue lightly. Serve in slices.