Rinse the Tongue and place it in a large heavy pot with water to cover. Simmer until just barely tender, about 1 1/2 hours. Remove the Tongue from the pot. Remove the connective tissues and peel off the skin. Set the Tongue aside. Reserve 1/2up of the cooking liquid.
Melt the butter in a heavy saucepan over medium heat. Add the carrots and onions and cook, stirring occasionally, until lightly browned, 10 minutes. Add the Tongue to the pot along with the ham, wine, 1/2up of the reserved cooking liquid, the tomatoes, bay leaf, thyme, salt and pepper. Simmer, covered, until tender, about 1 1/2 hours.
To serve, slice the Tongue and arrange it on a deep serving platter. Spoon the sauce over the top and sprinkle with parsley.