1. Heat the oven to 160°C/fan 140°C/gas 3. Toss the lamb with the seasoned flour. Heat 1 tbsp oil in a medium casserole, then fry the meat for 10 minutes, until dark golden brown all over. Transfer to a bowl. Splash in the ale and bring to a boil, scraping up all of the tasty brown bits from the bottom. Tip this over the meat then wipe the pan with kitchen paper.
2. Heat 1 tbsp oil then gently fry the vegetables with the thyme and bay for 10-15 minutes until turning golden here and there. Return the lamb and juices to the pan, top up with the stock, then season. Cover the casserole with a lid, leaving just a small gap to one side, then cook in the oven for 21/2 hours.
3. With 40 minutes to go, make the topping. Add ½ tsp salt to the flour in a large bowl. Rub in the butter with your fingertips until the mix looks like fine crumbs. Combine the milk, mustard, thyme and half of the egg, then tip into the bowl and bring to a soft dough. Knead a few times on a floured surface till just smooth, then pat the dough to about 3cm/1in thick and stamp into rounds. Squash together any trimmings and repeat. Don’t overwork the dough as it will make it tough.
4. Uncover the meat, stir gently and taste the sauce for seasoning at this point. Place the cobbler pieces on top, brush them with the remaining egg, then return to the oven until the topping is golden and lamb tender. Let the cobbler settle for 10 minutes before serving with your favourite seasonal greens.