Soak the tongues for 24 hours in cold water, changing the water several times. Heat the lard or butter in a small frying pan and cook the carrots, leeks, and turnips until golden, about 5 minutes. In a small bowl whisk together 4 tablespoons of the flour and 1/4 cup of boiling water. Pour the flour mixture into a large saucepan, then add the tongues, 4 quarts of water, 1 teaspoon of salt, the peppercorns, cloves, 2 tablespoons of the lemon juice, the carrots, leeks, turnips, and bouquet garni. Bring to a boil, cover, reduce heat to a simmer and cook until tender, about 1 1/2-2 hours,. Drain the tongues, reserving the cooking liquid. With a sharp knife, make an incision and peel off the skin on the tongues, discarding it. Cut the tongues into 3 long pieces. Return the cooking liquid to the saucepan and boil it hard, over high heat, until it reduces to 4 cups. In a medium-sized saucepan, melt 2 tablespoons of butter and whisk in the remaining flour. Cook for 2 minutes, then add the reduced stock. Cook, whisking constantly, until thickened. Stir in the mushrooms, tongue, remaining lemon juice, crÅme fraöche, and herbs, salt and pepper.
