Cook the tongue:

Cup of Yum
1. Rinse the tongue and place it in a large stockpot. Add enough water to cover it completely - I typically use 14 cups of water.
2. Bring the water to a boil. This should take about 20 minutes. When the water starts boiling, skim the foam off the top with a spoon. Lower the heat to a simmer. Add the bay leaves, peppercorns, and allspice.
3. Cook partially covered, turning the tongue every hour with two wide spatulas to ensure even cooking on all sides. Cook 3 hours for a 2-pound tongue and 4 hours for a 3-pound tongue.

To make the sauce:

1. Start making the sauce about 30 minutes before the tongue is ready. Heat the butter in a large, deep skillet over medium heat. Swirl to coat. Add the onions and cook, stirring occasionally, until golden, for about 10 minutes.
2. Add the mushrooms and cook, stirring, until soft, for about 5-7 minutes. If the pan becomes too dry, add a splash of broth.
3. Add salt, pepper, and beef broth. Bring to a boil over high heat. Lower the heat to a simmer, and cook, uncovered, for about 20 minutes to thicken the sauce and meld the flavors.
4. Mix the cornstarch with 2 tablespoons of water. Add this slurry to the sauce and stir until the sauce thickens. Turn the heat off, cover, and keep the sauce on the warm burner while you tend to the tongue.

Finish the dish:

1. Remove the cooked tongue to a cutting board. Allow it to cool for a couple of minutes until it is easier to handle, and then use your hands to peel off the skin.
2. Slice the tongue.
3. Arrange tongue slices on plates. If not using the sauce, sprinkle them with salt to taste (they were cooked in unsalted water to keep the meat tender). If using the sauce, spoon sauce on top of each slice, sprinkle the dish with chopped parsley, and serve.