First, make the pastry. Lightly toast the cumin seeds in a dry pan, then grind in a pestle and mortar. Put half in the bowl of a food processor along with the flour, turmeric, cayenne, and seasoning.
Add the cold, diced butter and pulse until the mixture resembles breadcrumbs. Add the water, and pulse until the dough just starts to come together. Tip out, form the dough into a ball and then flatten into a disc. Cover with clingfilm and chill for 1 hour.
Preheat the oven to Gas Mark 7, 220˚C, fan 200˚C. Spread out the peeled and chopped root veg and red onion on a roasting tray, and scatter with the crushed garlic, chopped chilli , the remaining ground cumin seeds and ground coriander. Season well and drizzle over the olive oil. Roast on the middle shelf for about 20 minutes, until the veg is tender and turning golden on the edges.
Remove from the oven, scatter over the spinach and allow it to wilt in the heat of the tray. Allow to cool, then stir through the coriander.
Divide the chilled pastry into 6 even pieces and, on a floured work surface, roll each out into discs roughly 16cm across. Top each with a mound of the roasted veg, adding crumbled goat's cheese or feta to each.
Make free-form pies by roughly folding the pastry up around the filling so that it's still visible in the middle.
Brush the pastry with milk and place the pies on baking trays. Cook for 20-25 minutes, until the pastry is golden and the filling is hot.