I used real key limes (they are tiny), but you can use ordinary ones and get the same result
For the crust
150g /5 1/2 oz graham cracker crumbs or rich tea biscuits, crushed
60g / 2oz golden caster sugar
3-g / 1oz finely chopped almonds
60g / 2oz melted butter
For the filling
6 large egg yolks
2 large egg whites
200ml / 7fl oz lime juice plus 2 tsp of zest
400g / 14oz tin of sweetened condensed milk
We had to use a disposable foil tart case, but it still tasted delicious
Preheat the oven to 190C / fan 170C / Gas 5. To make the crust combine the crumbs, sugar, almonds and butter in a bowl and mix well. Use the mixture to line the bottom and side of a 23cm / 9inch loose bottomed tart tin. Press firmly for the crumbs to stick and bake for 8-10 minutes. remove the crust to a rack and leave to cool.
Reduce the oven to 180C / Fan 160C / Gas 4. Beat the yolks with the condensed milk in a mixing bowl, then add the lime juice and rind. Whisk the egg whites to soft [peaks the fold through the mixture. Pour the filling into the crumb crust and bake in the oven for 15 minutes, transfer to a rack and cool, then chill.
Once chilled, served with whipped cream and fresh fruit.
To get ahead: The pie can be made up to a day ahead and stored in the fridge. It will keep for 2-3 days, but on holiday it never lasted that long!!