Instructions: Place the flour salt sugar and butter in a food processor and process until it resembles breadcrumbs.

Mix the egg and lemon juice and add through the feeder tube.

Switch off and gather the dough with your hands to a ball.

Wrap in clingfilm and chill for an hour.

Roll out to fit a 23cm shallow tart tin (with removable base).

Prick the base then refrigerate for at least two hours preferably overnight to prevent shrinkage.

Fill the pastry case with foil and baking beans and bake blind in a preheated oven (200C/400FMas Mark 6) for 15 minutes then remove the foil and beans and bake for further five minutes.

Remove and cool.

Lower the oven to 190C/375F/Gas Mark 5.

For the filling place the sugar citrus zest and juice in a bowl.

Mix 2 tbsp wine with the cornflour until a smooth paste is formed.

Add this with the remaining wine to the bo and whisk together.

Place the tart tin on a baking sheet near the oven (it is a very liquid filling the nearer it is to the oven the less slopping about).

Carefully fill with the wine mixture dot with the diced butter and bake in the preheated oven for about 25 minutes.

Some of the filling will still be wobbly: it firms up on cooling.

Serve barely warm.

Add a slug of Spanish brandy for even more of a punch. Scrub the oranges and lemons thoroughly before zesting.

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