Bombe Alaska with Neapolitan ice-cream

1.Combine half the cream, vanilla beans and vanilla seeds in a large saucepan, bring to the boil over medium-high heat. Meanwhile, whisk yolks and sugar in a large heatproof bowl until thick and pale (4-5 minutes). Pour cream mixture over yolk mixture, whisking continuously to combine, then return to a clean pan and stir continuously over low heat until mixture coats the back of a spoon thickly (10-15 minutes). Strain through a fine sieve into a bowl placed over ice, cool completely.

2.Whisk remaining cream until soft peaks form, fold through cooled custard. Divide into thirds, freeze one-third in an ice-cream machine according to manufacturer’s instructions and freeze until required.

3.Process raspberries in a food processor until smooth, then pass through a fine sieve to yield 250ml purée. Stir into one portion of the remaining custard, freeze in an ice-cream machine according to manufacturer’s instructions and freeze until required.

4. Melt chocolate in a heatproof bowl over simmering water, add to remaining custard, stir to combine. Freeze in an ice-cream machine according to manufacturer’s instructions. Meanwhile, remove vanilla and raspberry ice-creams from freezer to soften slightly.

5.Place a 2.5 litre tiffin mould (see note) in freezer until cold. Spoon large dollops of each ice-cream randomly into mould to create marbled pattern, tapping mould as you go to remove air bubbles. Smooth top, cover with plastic wrap and freeze for at least 8 hours.

6.For meringue, whisk eggwhites in electric mixer on high speed until stiff peaks form (1-2 minutes). Gradually add sugar, whisk continuously until stiff and shiny (4-5 minutes), add cornflour and vinegar, whisk to combine.

7.Dip mould in hot water and unmould onto a serving platter. Cover bombe with meringue using abstract stokes, ensuring there are no holes. Toast all over with a kitchen blowtorch set on medium until golden (1-2 minutes), cut into wedges, serve immediately.