Put the cardamom pods and seeds into a saucepan with the apricots, sugar and water. Bring to the boil then cover and simmer for 10 minutes until tender. Remove the cardamom pods, purée the apricot mixture and allow to cool.
Meanwhile, make the shortbread. Put the crushed cardamom seeds into the bowl of a food processor with the flours, sugar and butter and blitz until the mixture forms a ball. Alternatively, put the ingredients into a bowl and rub the butter in with your fingertips until the mixture resembles breadcrumbs. Squeeze the crumbs together to form a ball.
Tip the mixture into a 23 cm (9 inch) ungreased loose-bottomed flan tin and press into an even layer with your hands. Prick the surface and bake in a preheated oven, 160°C (325°F), Gas Mark 3, for 20–25 minutes until pale golden. Mark into thin wedges then sprinkle with a little sugar and leave to cool in the tin.
Whip the cream in a bowl until soft swirls form, then fold in the custard. Add the apricot purée and lightly swirl together until the mixture is marbled. Spoon into 4 glass tumblers. Cover and chill until required.
When ready to serve, put each tumbler on to a saucer and add 2 shortbread fingers.