To make the custard, put the milk, cream, vanilla pod and seeds in a heavy-based pan set over a gentle heat and cook until it nearly reaches the boil – but don’t allow to boil.
Meanwhile, put the egg yolks, sugar and cornflour in a large bowl and whisk together until pale and thickened.
Remove the hot milk and cream mixture from the heat and slowly whisk it into the egg mixture through a fine sieve until smooth.
Discard the vanilla pod and pour back into the pan, then set over a gentle heat. Cook, without allowing it to boil, until the custard coats the back of a wooden spoon, stirring continuously. Remove from the heat and leave to cool, covered with a piece of cling film pressed directly on the surface of the custard to prevent a skin from forming on top.
Meanwhile, prepare the fruit. Put the sherry in a large pan with the sugar and vanilla seeds and bring to the boil. Reduce the heat and simmer for 4–5 minutes, until syrupy, stirring occasionally. Stir in the frozen fruits of the forest and set aside until cooled, stirring occasionally. The fruits should defrost naturally in the hot syrup but still hold their shape.
Scatter the Madeira cake over the base of a 1.5 litre glass serving bowl. Spoon over the fruit and cover with the cooled custard. Chill for 1 hour, until the custard sets a little firmer, or up to 24 hours is fine.
When ready to serve, whip the cream in a bowl until you have achieved soft peaks. Put spoonfuls on top of the custard, then gently spread with a palette knife or the back of a spoon to cover the custard completely (or you can use a piping bag). Sprinkle over the toasted flaked almonds and pomegranate seeds and decorate with some spun sugar if liked, then place straight on the table to serve.