Put the eggs and sugar into a bowl and beat together with a wooden spoon until thick and creamy.

Pour the single cream into a small saucepan and heat gently until almost boiling then immediately

remove from the heat and pour on to the egg mixture, stirring vigorously. Leave the custard to cool.

Halve, stone and peel the avocados, then roughly chop the flesh. Puree with the orange zest and juice in a blender.

In a large bowl, whip the double cream until it forms soft peaks. Using a large metal spoon, fold in the avocado puree and the custard.

Turn into a large freezerproof container, cover and freeze until the mixture is frozen 2.5 cm (1 inch) around the edges. Scrape the mixture into a bowl and whisk until smooth, then return to the container, cover and freeze until firm.

Transfer to the main part of the refrigerator about 30 minutes before serving to soften.