Meanwhile, make the curd. Strain the citrus liquid that’s been infusing into a medium pan and bring to a gentle simmer. Mix the cornflour with 4 tbsp of cold water to slacken it. Bring the citrus liquid to the boil and quickly whisk in the cornflour to prevent any lumps. Turn down the heat and whisk for 2-3 minutes to thicken. Take off the heat and add the sugar, then the yolks, then the butter, Campari and vermouth. Whisk to combine, transfer to a bowl and cool for 5 minutes. Give it a whisk and transfer to the pastry case, then chill for 1 hour or until set.