You will also need a deep, fluted quiche tin with a loose base 9 inches (23 cm) in diameter and 1½ inches (4 cm) deep, lightly oiled.

1. The best way to make the pastry is in a food processor. To do this add all the pastry ingredients (except the egg white) to the bowl with 1 tablespoon water and process until it forms a firm dough. Then turn it out and knead lightly before placing in a polythene bag and leaving in the fridge for 30 minutes to rest.
2. To cook the pastry base, pre-heat the oven to gas mark 6, 400°F (200°C) and place a solid baking sheet inside to preheat as well. Now roll out the pastry as thinly as possible and carefully line the quiche tin, pressing the pastry around the base and sides so that it comes about ¼ inch (5 mm) above the edge of the tin. Then prick the base with a fork and brush it all over with the reserved egg white, which you should lightly beat first.
3. Bake on the baking sheet on the middle shelf for 20 minutes, then, as you remove it, turn the temperature down to gas mark 4, 350°F (180°C).
4. To make the filling, grate the zest from 6 of the lemons, and squeeze enough juice to give 10 fl oz (275 ml). Now break the eggs into a bowl, add the sugar and whisk to combine, but don't overdo it or the eggs will thicken. Next add the lemon juice and zest followed by the cream, and whisk lightly. Now pour it all into a 2 pint (1.2 litre) jug.
5. The easiest way to fill the tart is to place the pastry case on the baking sheet in the oven, and then pour the filling straight into the pastry (this avoids having to carry the tart to the oven and spilling it). Bake for about 30 minutes or until the tart is set and feels springy in the centre. Let it cool for about half an hour if you want to serve it warm. It's also extremely good served chilled. Either way, dust it with icing sugar just before serving and serve with well-chilled crème fraîche.