Lemon Tart

Rub the cold butter into the flour, the 60g of icing sugar and the fine salt with your fingertips, until the mixture looks like coarse breadcrumbs with no butter pieces bigger than a pea.

Stir the egg yolk into the 2 tbsp of ice-cold water and pour it over the crumbs.

Cut the liquid through the mixture with a table knife until it starts to clump.

Press the clumps together with one hand into a single lump with no dry flour left, using as few movements as you can. Sweet pastry worked like bread dough builds gluten, and gluten is what makes a case shrink down the sides of the tin and bake tough.

Flatten the dough into a disc about 2cm thick, wrap it and refrigerate for 1 hour.

Roll the dough out on a lightly floured worktop to a round about 30cm across and 3mm thick, turning it a quarter turn after every couple of passes so it does not stick.

Line a 23cm loose-bottomed tart tin, easing the pastry down into the corner with a knuckle rather than stretching it across. Pastry pulled tight over the base pulls back as it bakes and the sides slump.

Leave the excess hanging over the rim and trim it only after the case is baked. Every case shrinks a little, and trimming it flush now is what leaves you with a tart too shallow to hold the filling.

Prick the base all over with a fork.

Chill the lined tin for 30 minutes.

Heat the oven to 180C/350F.

Line the chilled case with a sheet of baking paper and fill it to the top of the sides with baking beans.

Bake for 20 minutes.

Lift out the paper and beans and bake for a further 8-10 minutes, until the base is dry, sandy and pale gold with no grey damp patches left.

Beat the egg white loosely with a fork.

Brush the inside of the hot case thinly all over with the white.

Return it to the oven for 2 minutes, until the white has set to a dull film. That film seals the hairline cracks a liquid filling would otherwise leak through, and a leaked tart welds itself to the tin.

Turn the oven down to 150C/300F.

Whisk the 4 eggs and the caster sugar together in a bowl until smooth, stirring rather than beating so no air goes in.

Whisk in the lemon zest and the 150ml of juice.

Whisk in the double cream.

Skim any foam off the surface with a spoon, since bubbles bake into a mottled, freckled skin.

Set the tart case on a baking tray and slide it onto the oven shelf before it is filled.

Pour the filling in at the open oven door, right up to the pastry rim. Carrying a full tart across a kitchen is how it ends up on the floor.

Bake for 30-35 minutes, until the filling is set to the edge and only the middle 5cm shivers when you tap the tray.

Turn the oven down to 140C/275F if the surface starts to blister or bubble at the edge. That is the custard boiling, and a boiled lemon filling sets grainy and weeps water under the slice.

Cool the tart in its tin on a rack for at least 2 hours, until it is cold right through. It goes on setting the whole time it cools.

Trim the pastry standing above the rim with a small serrated knife, sawing outwards and downwards.

Lift the tart out of the ring.

Dust the surface with icing sugar.

Cut with a knife dipped in hot water and wiped dry, cleaning it between every slice.