First, make the pastry. Combine the flour, spices, sugar and 1 tsp salt. Rub in the butter and shortening with your fingers until the mixture resembles breadcrumbs. Whisk 1 egg and the vinegar together, then tip into the flour mixture. Bring together into a dough using your hands, adding 3-6 tbsp water if needed until just pliable. Knead for 3-5 mins, then cover and chill for 30 mins. Remove from the fridge 30 mins before you’re ready to use.
Meanwhile, heat the oil in a pan and fry the onion over a medium heat for 10 mins until softened. Add the tomato, thyme, garlic, chilli, if using, and ginger. Fry for a further 3 mins. Mix all the spices with a few tablespoons of water, then add to the pan. Fry for another 5 mins until the water evaporates and the spices are fragrant.
Add the turkey and fry for 5 mins. Pour in the stock, then reduce the heat and simmer for 10-15 mins until most of the liquid has reduced. Remove from the heat and leave to cool completely. Chill until ready to use. Will keep chilled for up to 24 hrs.
Heat the oven to 180C/160C fan/gas 6. Roll the chilled pastry out on a floured surface or sheet of baking parchment (this helps prevent the turmeric from staining the surface) to a 4mm thickness. If it starts to crack, press small pieces of the pastry into the gaps to fill. Using a 15cm-diameter bowl as a template, cut out as many circles of pastry as you can, then re-roll the offcuts and repeat until all the pastry has been used. You should end up with about 10 circles. Transfer to a baking tray lined with baking parchment.
Working with one pastry circle at a time, spoon 2 tbsp of the turkey curry filling onto one side of the circle, leaving a 2cm border. Beat the remaining egg with the milk and brush onto the border. Fold one half of the pastry over the other to form a semicircle and enclose the filling. Press the edges together, seal with a fork and prick the top all over.
Bake for 20-25 mins, or until the pastry is firm. Leave to cool slightly and serve. After cooling completely, will keep in the freezer for up to three months.