Preheat the oven to 180C/350F/gas 4.
Grease the tart tin with butter.
To make the pastry sift the flour and salt into the mixing bowl or food processor bowl.
Add the butter and then rub it in (or process if using food processor) until the mixture resembles fine breadcrumbs.
Place the egg yolk in a cup and add the ice cold water and whisk together.
Add to the pastry mix and bring together to make a dough adding more water if the dough is too dry. If using a processor add the egg mixture and whizz until the mixture forms a ball of dough.
Wrap the dough in clingfilm and place in the fridge for 30 minutes.
Remove the chilled pastry from the fridge, place on a lightly floured work surface and roll out to 2mm thick.
Line the tart tin, trim the edges and place in the fridge for 20 minutes.
Remove the tart tin from the fridge and prick the bottom all over with a fork.
Scrunch up a large piece of baking paper, open it out and place over the pastry. Fill with baking beans and bake in the preheated oven for 15 minutes.
Take out of the oven, remove the paper and baking beans and brush the pastry with the beaten egg. Return to the oven for a further 10 minutes. Set aside to cool. Leave the oven on.
Place the gooseberries in the saucepan with a little water and bring to a boil. Simmer until tender. Take off the heat and allow to cool slightly. If using tinned gooseberries simply drain to remove the syrup.
Place the gooseberries in the food processor and blend to a smooth, sloppy paste.
Place the eggs and sugar in a large mixing bowl and beat with the electric hand whisk until pale and voluminous.
Add the gooseberry purée to the eggs and sugar mixture and continue to whisk until fully incorporated.
Add the remaining ingredients and stir thoroughly.
Pour the mixture into the prepared pastry case and bake in the preheated oven for 30 minutes or until the filling is set.
Remove from the oven and allow to cool to room temperature before removing the tart tin and transferring to a serving plate.
