Method

1. First make the cake: heat oven to 160C/fan 140C/gas 3. Lightly butter a Swiss roll tin and line the base with non-stick baking parchment. Put the whole eggs, egg yolks and caster sugar in a bowl and whisk with an electric hand whisk for 8-10 mins until light and fluffy. Meanwhile, melt the chocolate and butter in a bowl over a pan of almost simmering water, stirring occasionally.

2. When the whisked egg mixture is light and fluffy, gently fold in the flour with a large metal spoon or the whisk blades, taking care not to lose too much volume. Beat a small amount of the egg mixture into the melted chocolate, then gently fold the chocolate into the remaining egg mixture. Pour into the prepared tin, then tilt the tin from side to side until even and the corners are filled. Bake for 10 mins until firm, then leave to cool completely.

3. Line a 1-litre freezer-proof pudding basin with cling film. Cut a small circle of sponge cake to fit the base then cut triangular pieces to line the sides. Fill any gaps with trimmings and save the remaining sponge for later. Place the bowl in the freezer to firm up the sponge.

4. Make the ice cream: slice the vanilla pod in half lengthways and remove the seeds. Put the milk, vanilla seeds and pod, orange zest, caster sugar and cream into a medium pan and bring to the boil. Meanwhile, whisk the egg yolks together in a large bowl. Pour the hot cream mixture slowly on to the eggs, whisking all the time. Return the mix to a clean pan and stir constantly over a gentle heat for about 5 mins until the mixture has just thickened. Pass through a sieve and leave to cool for 30 mins. Churn in an ice-cream machine (or make by hand, see 'Try' below). Add the marmalade and continue to churn for another 10 mins until thick.

5. Scoop the ice cream into the cake-lined bowl, leaving a central indent for the sorbet layer. Sit a small bowl in the top of the ice cream to make a smooth indent for the sorbet later to sit in. Freeze for at least 1 hr, until just firm.

6. Fill the centre of the bombe with orange sorbet, cover the entire base of the bowl with a layer of sponge, cover with cling film and return to the freezer until needed, or at least 8 hrs ahead. This can be done well in advance and that’s all the really hard work done.

7. To make the hot chocolate sauce, grate the chocolate into a bowl and add the golden syrup, butter and warm water. Melt over a pan of just simmering water until melted, stirring occasionally.

8. About 20 mins before serving, heat oven to 230C/fan 210C/gas 8. Whisk the egg whites and a pinch of salt in a large clean bowl until stiff but not dry. Whisk in the sugar, a little at a time, bringing it back to stiff peaks before each addition. Turn the bombe out onto an ovenproof serving dish and remove the cling film. Spoon the meringue all over the bombe to completely seal it. Using the back of the spoon or a palette knife, pull the meringue into dramatic swirls. Bake for 10-15 mins or until golden. Reheat the chocolate sauce over a pan as before or in a microwaveable bowl for 1 min on Low, stirring halfway through. Take the Chocolate orange bombe Alaska to the table immediately and serve sliced, drizzled with the hot chocolate sauce.