To make the curd cheese, place the milk and single cream in the large saucepan and bring to the boil. Reduce the heat to a simmer and add the lemon juice. 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 the large 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 bowl, cover with clingfilm and refrigerate. (Reserve the liquid in the bowl (whey) and store in the fridge - it is a good substitute for buttermilk so 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 large mixing bowl.
Cut the butter into very small chunks, add them to the bowl and stir them in.
Add the cold water and bring together to a wet dough with a lumpy consistency.
Cover with clingfilm and place in the fridge for 30 minutes.
Place the dough on a floured work surface and shape into a rectangular block.
Roll the dough to a rectangle three times longer than it is short, keeping the edges straight and even. The rolled-out pastry should have a marbled effect from the lumps of butter.
Fold the top third down to the centre, then the bottom third up and over that.
Give it a quarter turn and roll out again to the original sized rectangle.
Repeat the folding, turning and rolling out 3 more times or until the marbling effect has disappeared. Fold once more and place in the fridge for 30 minutes.
Remove the dough from the fridge and place on a lightly floured work surface.
Roll out the dough and line the tart tin.
Place the lined tart tin in the fridge for 20 minutes while you make the filling.
Place the eggs and sugar in a large mixing bowl and beat with the electric hand whisk until thick and pale in colour.
Add the curd and continue whisking until fully incorporated.
Add the remaining ingredients and stir in thoroughly.
Remove the tart tin from the fridge and pour the filling into it.
Place in the oven and bake for 35-40 minutes until the filling is set with just a hint of a wobble.
Remove from the oven and allow to cool for 20 minutes before removing the tart tin and transferring the tart to a serving plate. Leave to cool to room temperature before serving.
