Preheat the slow cooker if necessary; see the manufacturer's instructions. Put the apricots, orange rind and juice and sugar into the slow cooker pot and pour over the water. Cover with the lid and cook on low for 3–4 hours or until the apricots are plump.
Lift the pot out of the housing using oven gloves and leave the apricots to cool, then purée with a stick blender or transfer to a liquidizer and whizz until smooth.
Fold the custard and yogurt together until just mixed, then add the apricot purée and very lightly mix for a marbled effect. Spoon into the glasses and serve with dainty biscuits.