Preheat the oven to 170C/325F/gas 3.
Grease the tart tin with butter.
To make the pastry sift the flour and salt into the large mixing bowl or food processor bowl.
Add the butter and rub in (or process if using food processor) until the mixture resembles fine breadcrumbs.
Place the egg yolk in the cup, 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.
Roll out the pastry on a lightly floured work surface and line the tart tin.
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 until the pastry is cooked through. Allow to cool while you make the filling.
Place the milk in the small saucepan with the lemon peel and bring to the boil. Take off the heat immediately and allow to infuse for half an hour.
Strain the milk into the medium saucepan and heat.
Add the ground rice and simmer for 15 minutes, stirring all the time until thickened. Leave to cool a little.
Place the butter and sugar in the large mixing bowl and beat with the electric hand whisk until light and fluffy.
Add the beaten eggs and milk and ground rice mixture and beat with the electric hand whisk to a smooth batter.
Pour the filling into the pastry shell and scatter with the currants.
Place in the oven and bake for 20 to 25 minutes or until the filling is set but retains a slight wobble and the top is golden.
Remove from the oven and allow to cool completely before removing from the tin and transferring to a serving plate.
