Spread the jam over the cake slices and arrange them in the bottom of a large glass trifle bowl (so you can see all those beautiful layers!). Pour the sherry evenly over the cake and let it soak in for about 10 minutes.
Scatter half of the fresh berries over the soaked cake layer. Reserve the prettiest ones for the top.
To make the custard, heat the milk with the vanilla pod and seeds (or extract) in a saucepan until just about to boil. Remove from heat.
In a large bowl, whisk together the egg yolks, caster sugar, and cornflour until pale and creamy. Gradually pour in the hot milk, whisking constantly.
Return the mixture to the saucepan and cook over medium-low heat, stirring constantly, until thickened—about 8-10 minutes. Don't let it boil or the eggs will scramble!
Pour the custard through a sieve over the cake and berries. Cover with cling film (press it directly onto the surface to prevent a skin forming) and refrigerate for at least 3 hours, or overnight.
When ready to serve, whip the double cream with the icing sugar until soft peaks form. Spread or pipe it over the set custard layer.
Decorate the top with the remaining fresh berries, toasted almonds, and maybe a little grated chocolate or a dusting of cocoa powder if you're feeling fancy. Serve with a big spoon and watch everyone's faces light up!
