Preheat oven to 120C.
Season the beef shin with sea salt and freshly ground black pepper. Heat a wide heavy base frying pan on the stove. Add a good drizzle of oil and fry the diced beef in batches, ensuring you get lots of colour on the meat. Transfer the browned beef to a casserole dish.
Add the shallots, face down, to the pan with a little more oil. Transfer to the casserole dish. Add the red wine to the pan and boil the red wine to deglaze the pan, reduce by half and add to the casserole dish.
Top up the dish with the beef stock, garlic and thyme. Add a lid and place in the oven for 6 hours.
Prepare the dumplings. Add the flour and suet to a bowl, season with plenty of salt and pepper. Add 150ml of water and chopped tarragon to the mixture. Bring together by hand to form a soft dough.
Remove the casserole from the oven. Strain the stew so you have the beef and shallots separated from the cooking liquor. Reduce the cooking liquor in a large pan and reduce by around a third. Return to the beef in the casserole dish and dot the pickled walnuts around the stew.
Divide the dumpling mixture into 7-9 small dumplings and place on the surface of the stew.
Reduce the temperature of the oven to 170C. Place the lid on the casserole dish and bake for 20 minutes. Remove the lid and bake for a final 15 minutes.
Serve with winter greens and Dijon mustard.
