In a large pot combine the meat, the spice bag and enough cold water to cover. Bring to a boil, reduce heat and simmer 2 hours. Add vegetables and salt and return to a simmer
. Continue to simmer until fork-tender, 30 minutes to 1 hour longer.
For the Horseradish Cream: In a small bowl combine sour cream and horseradish; season, to taste, with salt, pepper and hot sauce.
To finish, remove corned beef to a carving board and slice against the grain. Transfer to a large, warmed, deep platter. Drain broth and reserve for soup, if desired. Arrange vegetables around meat and serve. Pass the horseradish cream for guests to help themselves.