To make the curd cheese, bring the milk and single cream to a gentle simmer in the large saucepan, then add the lemon juice. Lower the heat and stir gently, and watch the milk separate into curds (white lumps) and whey (pale liquid). Remove from the heat and leave to cool.
Place the sieve over a large mixing bowl and line with the muslin.
Pour the separated milk into the sieve and leave to drain for at least 2 hours.
Scrape the curd cheese from the cloth, place in the medium mixing bowl and refrigerate. (Reserve the liquid (whey) and store in the fridge - it can be used for other recipes such as scones or soda bread).
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 in (or process if using food processor) until the mixture resembles fine breadcrumbs.
Break the egg into 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 in clingfilm and place in the fridge for 30 minutes.
On a lightly floured work surface, roll out the pastry and line the tart tin with it.
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. Remove from the oven and set aside to cool.
Meanwhile, make the filling. Place the butter and sugar in a medium mixing bowl and beat with the electric hand whisk until light and fluffy.
Add the beaten egg and beat in thoroughly.
Add the nutmeg and ginger and then beat in the curd cheese.
Add the currants and stir in.
Pour the curd filling into the pastry shell tin and bake for 35-40 minutes until the pastry is golden and the filling is set.
Take out of the oven and allow for 10 minutes before removing the tin and transferring to a serving plate. Allow to cool to room temperature before serving.
