Place the dried mushrooms in a small pot and cover with half the beef stock. Bring to boil and simmer until very tender and liquids reduce by one-third, 15 minutes.
Meanwhile heat the olive oil, a couple turns of the pan, over medium-high heat. Sprinkle the meat with salt and pepper and brown half the meat until evenly crusted all over. Remove the browned meat to a plate. Repeat for the remaining meat, using more oil as needed.
Add the butter to the meat drippings and melt. Add the thyme and portabellas, cook until well browned, 10 to 12 minutes. Season with salt and pepper, add the garlic and onions and cook 5 minutes more. Add the wine and deglaze the pan. Chop and add the porcinis and their liquids, the remaining 2 cups of stock and Worcestershire. Cover and roast until tender, 2 hours. Cool and store for a make-ahead meal. Reheat in 325 degrees F oven until heated through, or on the stovetop, partially covered, over a medium flame. Toss the parsley and celery with the lemon juice, EVOO and some salt and pepper, then mix in the cheese. Garnish the stew with the celery salad on top.