Heat a large frying pan over a medium heat, add 2 tablespoons of the oil then add the onions, carrots, celery and garlic and fry for a few minutes. When they begin to pick up some light golden brown colour, transfer to a large casserole dish, preferably with a lid.
Sift the flour onto a plate and season with salt and pepper. Toss the beef in the seasoned flour until coated and shake off to remove any excess. The flour is here to thicken the sauce, so you don’t want too much flour in the first place or you’ll end up with a less than appetizing consistency.
Crank the heat up high, then add the remaining rapeseed oil to the frying pan. In batches, fry the beef for 1 minute on each side until browned all over. Add the beef to the vegetables in the casserole dish.
Add a splash of the ale to the frying pan and use it to gently prize off any cooked-on pieces of food, then pour it all into the casserole dish. Add in the remaining ale, the beef stock and rosemary. Bring to a simmer then put it in the oven and cook for 3–4 hours, or until the meat is falling apart. Season to taste with sea salt and black pepper.
When the beef is 30 minutes from being done, put the potatoes into a saucepan and pour in enough water so that they are just submerged. Add a pinch of salt then bring the pan of water to the boil. Simmer for 12–15 minutes until the potatoes are tender, then drain and return to the pan over the heat for a couple of minutes. This will drive off any excess moisture and give a lighter, fluffy mash.
Mash until silky smooth before stirring in the butter and milk. Season to taste with salt and pepper and serve with a generous helping of the beef shin.