Seville orange tart

Method

1. To make the pastry, sift the flour, icing sugar and a small pinch of salt into a food processor, add the chilled butter and the orange zest. Pulse until it looks like fine breadcrumbs, then tip into a mixing bowl.
2. Mix the egg yolk with the orange juice, add to the bowl, then stir with a round-bladed knife until the mixture starts to come together into a ball. Turn out onto a lightly floured surface and knead briefly until the mixture forms a smooth dough.
3. Roll the pastry out thinly on a lightly floured surface, then use to line a lightly greased, 4cm deep, 23cm loose-bottomed flan tin. Prick the base all over with a fork, then chill for 20-30 minutes.
4. Preheat the oven to 200°C/fan180°C/gas 6. Line the pastry case with a crumpled sheet of baking paper and a thin layer of beans or rice, then blind-bake for 12-15 minutes until the edges of the pastry are biscuit coloured. Carefully remove the paper and beans/rice, then return the pastry case to the oven for 3-4 minutes.
5. Beat the egg white until slightly frothy, then brush it over the base and sides of the pastry case. Return the case to the oven for another 1-2 minutes until set. Remove and leave to cool. Turn the oven down to 120°C/fan100°C/gas ½.
6. For the tart filling, finely grate the zest from the oranges, then set aside. Squeeze the juice from the seville oranges (or from the lemons and 2 of the zested oranges) to give 180ml. Break the eggs into a bowl, add the caster sugar, then whisk lightly with a fork until just mixed but not frothy. Strain in the citrus juice, add the double cream, then mix briefly. Strain through a sieve into a large measuring jug, then 
stir in the citrus zest.
7. Partly pull out the shelf of the preheated oven, slide the pastry case onto it, then pour in the filling. Carefully slide the shelf back in and bake for 40-45 minutes or until just set. It should still be a little wobbly in the centre, but will firm up as it cools. Remove and leave to cool, but don’t refrigerate. This is best served, cut into wedges, on the day it’s made.