Sweet, tart and delicious! You can use key limes if you are lucky enough to get them or substitute with large limes. Add a drop of green food colouring if you like. It's best if you prepare this a day in advance.
To make the base: In a bowl stir together the digestive biscuit crumbs and 2 tablespoons sugar; stir in the butter and mix well to combine. Pat the mixture into the bottom and about 1.5cm up the side of a buttered 25cm springform cake tin.
Bake the base in a preheated oven for 8 minutes. Transfer the tin to a rack and cool.
To make the cheesecake filling: In a large bowl with an electric mixer, beat cream cheese and 150g caster sugar until smooth. Beat in the eggs, one at a time, beating well after each addition. Beat in the soured cream, flour, lime juice and vanilla. Beat the mixture until it is smooth.
Pour the filling over the base. Bake the cheesecake in the preheated oven for 15 minutes, then reduce the temperature to 120 C / Gas mark ½ and bake for 50 to 55 minutes longer, or until centre is just set and no more.
Let the cheesecake cool on a rack, then chill it, covered, overnight. Remove the cheesecake from the pan and transfer it to a cake stand.
Garnish with whipped cream and thin slices of lime.