Key lime pie

Preheat the oven to 180°C (160°C fan, gas mark 4).

To make the  pie crust, mix the biscuit crumbs with the melted butter into a bowl by hand and press into a buttered deep 25cm/10" loose bottomed, preferably fluted, tart tin. If you don't have one of the latter, use a spring form tin of the same size and just press the crumbs two-thirds of the way up the side.

Bake in the preheated oven for 10-15 minutes. Remove from the oven and cool.

For the filling, beat the egg yolks in a bowl until light and fluffy, then beat in the condensed milk and lime zest and juice.

In another bowl, whisk the eggs whites and caster sugar until firm, and then gently fold into the lime mixture, using a large metal spoon.

Completely fill the biscuit base with the lime mixture and bake in the preheated oven, at the same temperature for 20-25 minutes until set and slightly browned around the edges. Leave to cool. Don't worry if the filling sinks slightly.

Loosen the edges of the tart, remove the tin and transfer to a serving plate. Dust the top with icing sugar then decorate with lemon slices and fresh mint leaves.