10 ml (2 tsp) powdered gelatine
30 ml (2 tbsp) water
100 g (4 oz) digestive biscuits, crushed
50 g (2 oz) ginger biscuits, crushed
75 g (3 oz) butter or block margarine, melted
275 g (10 oz) ripe bananas, peeled
40 g (1 1/2 oz) soft brown sugar
thinly pared rind of a thin-skinned lemon
45 ml (3 tbsp) lemon juice
1 egg white
142 ml (5 fl oz) carton double cream
50 g (2 oz) chopped walnuts