Add the cubed, chilled butter and sugar. Blitz quickly until the butter has broken up and then add the eggs.
As soon as the pastry has come together remove from the mixer. Mould together. Wrap in cling film and chill in the fridge.
Roll out the pastry and line the tin. Chill for a further 30 minutes, then blind bake in a fan oven at 180°C for 15 minutes.
For the Filling
Place the farro, milk, lemon zest and vanilla pod in a solid steam container and cook on 100°C for 40 minutes.
Add the ricotta, sugar and mixed peel and stir gently to combine.
Place the cream, sugar and salt in a heavy bottomed pan. Bring to the boil then remove from the heat and allow to infuse for 5 minutes. Whisk the egg yolks and slowly add the warmed cream.
Pour the custard into the ricotta filling and pour into the prepared tart shell. Bake until set on 150°C (approximately 25-30 minutes).