Gelato alle Amarene Tie the cherry stones in a piece of cheesecloth. Put the cherries in a saucepan and add half the sugar, the cherry stones, the zest and juice of the lemon, vanilla bean and sufficient water to barely cover the cherries. Simmer for 30 minutes. Set aside to cool. Discard the cherry stones. Push the sauce through a sieve into a bowl. In the top of a double boiler, beat the egg yolks with the remaining sugar until the mixture falls from the beater in a ribbon. Add the milk. Place over simmering water and cook, without boiling, until the custard thickens enough to coat a spoon. Remove from the heat and set aside to cool. Freeze the mixture in an ice-cream machine and churn until set. Transfer the ice-cream to a shallow serving bowl. Pour the morello cherry sauce over it and serve.