Before you start
- Humid conditions will cause the meringue to fail, so don't attempt this on a rainy or cloudy day, or if you are cooking something steamy in the kitchen
- All of your equipment must be scrupulously clean and dry with no traces of fat or grease
- When you separate the eggs, if you get any yolk in the white, throw it away
- Older eggs are better than super-fresh ones, and they must be at room temperature
Make the pastry
Add the sugar and the egg yolk to the flour and stir them together. Break the butter into small pieces and stir them in, then rub it in with your fingertips until the mixture looks like breadcrumbs. Stir in just enough water so that the mixture holds together as a dough. Refrigerate for half an hour.
When the pastry has rested, roll it out into a disc on a floured surface. Grease the inside of your baking tin with butter, then drape the pastry over your rolling pin and gently roll the pastry into the tin. This pastry is very delicate, so you'll need to be careful with it. Push the pastry down into the tin so it goes right into the edges. Trim off the excess pastry.
Preheat the oven to 180℃ (350℉). Prick the bottom of the pastry all over with a fork, then line it with foil. Pour in dried beans or lentils (this is just to stop the bottom of the pastry from puffing up while it bakes), and place in the oven for 15 minutes. Remove the beans and the foil, and bake for a further 10 minutes.
Make the filling
Cut the butter into small chunks. Mix together the cornflour and sugar in a small saucepan. Add the zest of the 2 lemons, and then gradually incorporate the juice of the 2 lemons and the juice of the orange. Heat the mixture and keep stirring until it begins to bubble and thicken. Once it is thickened, remove from heat and add the butter a bit at a time. If the mixture seems too thick, add a drop of hot water. When all the butter is mixed in and melted, add the egg yolks and stir vigorously until you have a nice thick smooth mixture. Set aside.
Make the meringue
Pour the egg whites into a clean stainless steel, glass or ceramic bowl, and whisk until you have stiff peaks (this is when a spoonful of the mixture will hold its shape and not fall off the spoon). Whisk in the sugar and cornflour a bit at a time.
Assemble the pie
Your oven should still be on. If not, preheat it to 180℃ (350℉). Spoon the lemon filling mixture into the pastry case and smooth it into an even layer. Place spoonfuls of the meringue mixture around the edge, and then fill in towards the centre. Run a fork over the outside to form ridges and peaks that will catch the heat.
Bake for 20 minutes, then turn off the heat but leave the oven door open. Leave it for half an hour, then take it out of the oven and allow to cool on a wire rack for 30-60 minutes.
Now you can eat it. But be warned, meringues do not keep well, so you'll need to eat the whole thing on the day it's made. Tragic, eh?