Method
1 Preheat your oven to 195C.
2 Lightly brush the souffle moulds with butter and dust with caster sugar, then place them to one side.
3 Whisk together the egg yolk and sugar in a medium-sized bowl until it is pale and creamy.
4 Whisk together the egg whites, then after a minute add the caster sugar. Continue to whisk until the mixture is firm and stiff.
5 Add the lime juice and zest to the yolk mixture and mix well, add a little of the whites to the yolk mixture, mix, then fold in the remaining egg whites.
6 Spoon the mixture to just over the rim of the moulds, then place the souffles in a baking tray and fill with hot water halfway up the sides. Bake for 12 to 14 minutes, or until the souffles are well rizen yet still soft in the middle.
7 Quickly dust with icing sugar and serve immediately.