How to Make It
Preheat the oven to 350°. Put the flour in a large bowl and season generously with salt and pepper. Add the lamb cubes in 4 batches, tossing to coat thoroughly.
In a large enameled cast-iron casserole, heat 2 tablespoons of the oil until shimmering. Add one-fourth of the lamb cubes and cook over moderately high heat until browned, about 6 minutes; transfer to a plate. Brown the remaining floured lamb in 3 batches, adding 2 tablespoons of oil to the pot per batch. Reduce the heat if the casserole bottom darkens too much.
Return all of the lamb to the casserole. Add the wine and vinegar and bring to a boil. Add the stock and tarragon and return to a boil. Season with salt and pepper. Cover the casserole and braise the stew in the oven for about 1 hour, or until the meat is nearly tender.
Add the carrots, parsnips, potatoes, turnips, fennel and shallot to the lamb stew. Season with salt and pepper and bring to a boil, stirring to distribute the vegetables. Cover the casserole, return it to the oven and cook until the meat and vegetables are tender, about 1 hour longer. Season with salt and pepper. Stir in the parsley and fennel fronds and serve the stew in deep bowls.