Photo: Jan Baldwin
Line a 7cm-deep 22 x 10cm loaf tin with clingfilm so it overhangs the edges all the way round. Whizz the raspberries in a food processor with half the icing sugar. Sieve the purée into a bowl, discarding the pips.
Whip the cream with the rest of the icing sugar to soft peaks. Fold the custard into the cream and divide between two bowls. Stir the raspberry purée into one bowl.
In another bowl, whisk the egg whites to soft peaks. Fold half the egg whites into each custard mixture. Spoon the two mixtures into the prepared loaf tin, alternating spoonfuls of each mixture. Reserve 2 tbsp mixture. Use a skewer to gently swirl the mixtures together.
Pour the sherry into a shallow bowl. Dip both sides of the sponge fingers into the sherry and place on top of the mixture in two layers. Finish with a thin layer of the leftover mixture. Cover with the clingfilm and freeze overnight.
Gently melt the sugar in a small pan. When it has turned to a golden caramel, stir in the flaked almonds and tip on to a sheet of nonstick baking paper. Leave to set.
Transfer the terrine from the freezer to the fridge 30 minutes before serving. Tip it out of the tin, remove the clingfilm and scatter with the praline, broken up, and the extra raspberries. Slice to serve.