Iced Lime Parfait

In a pan, boil the lime juice and zest to reduce by 3/4. Cool

Put the egg yolks, sugar and reduced lime juice in a heatproof bowl over a pan of simmering water. Whisk until the mixture is thick, light and at least doubled in volume

Remove from the heat and continue to whisk until the mixture cools to room temperature.

Fold in the cream and Marsala

Whisk the egg whites until they can form stiff peaks. Fold into the mixture. Spoon the mixture into glasses and leave to set in the freezer for at least 2 hours