handful fresh blueberries
2 limes, finely grated zest
125ml/4½fl oz lime juice
210ml/7½fl oz condensed milk
50g/2oz caster sugar
80g/3oz caster sugar
½ tsp cream of tartar
pinch salt
½ tsp vanilla extract
175g/6oz digestive biscuits
80g/3oz butter
whipped cream
3 large free-range eggs, separated