Add the flour, baking powder, pinch of salt, and most of the herbs into a food processor and blend to combine. Add the butter and blitz for 10 seconds until the mixture resembles fine crumbs.
Whisk the milk and egg together in a bowl. Set aside 1 tablespoon, then add the rest to the crumb mixture. Mix with your hands to form a dough. Add the potatoes, veg, cheese, nuts, and stuffing, if using, and knead until evenly mixed.
Preheat the oven to gas 9, 240°C, fan 220°C, and line a baking tray with baking paper. Tip the dough onto a floured work surface and press into an 18cm disc, about 2.5cm thick. Sprinkle flour in a shallow bowl, then use a 7cm round cutter to stamp out 4 scones, dipping the cutter in the flour between each one. Don’t twist the cutter, as this can seal the edges and stop the scones from rising. Knead the scraps together and stamp out 2 more scones.
Put the scones on the lined tray. Brush the tops with the reserved egg and milk mixture, then sprinkle over the remaining herbs. Bake on the middle shelf, reducing the heat to gas 7, 220°C, fan 200°C, for 15–17 minutes. Rotate the tray once during cooking, then bake until the scones are risen and cooked through. Cool on a wire rack for 20 minutes. Split and serve with leftover roast turkey and cranberry sauce.
