Bring the beef to room temperature. Pat dry and sprinkle with salt. Dredge the beef lightly in flour, shaking off the excess.
Heat about 1 tablespoon EVOO in a Dutch oven over medium-high heat. Brown half the beef and transfer to a plate. Add another 1 tablespoon EVOO to the pot and brown the remaining beef. Return all the beef to the pot and add the stock and enough water to cover the beef. Stir in the garlic and bay leaf and bring to boil. Reduce the heat to medium-low, partially cover the pot and simmer for 2 hours. Stir in the red wine, tomato paste and pepper and cook until the beef is tender enough to fall apart and the sauce is thick, 2 to 3 hours more.
When the beef is almost finished cooking, cook the potatoes in a pot of boiling water until tender, 12 to 15 minutes. Drain and return to the hot pot. Cut the Taleggio into cubes and mash into the potatoes with enough milk to reach the desired consistency. Stir in the sage and season with salt and pepper.
Divide the beef and sauce among bowls and sprinkle with parsley.
Cook's Note: The beef stew can be covered and refrigerated for a make-ahead meal. Reheat gently, adding water as needed to thin the sauce.