Peel and dice 1 medium carrot and 1 small parsley root into half-inch (1.5 cm) cubes. Peel and roughly chop 1 small onion.
Clean and rinse 1 beef tongue under running water. Place it in a pot and cover it with cold water. Add the diced vegetables.
Cover the pot and bring it to a boil. If foam forms on the surface, skim it off with a spoon. Once the water comes to a boil, reduce the heat to low, add 1 Tablespoon lemon peel, 2 pieces bay leaves, 5 pieces allspice, 10 pieces peppercorn, ½ Tablespoon dried thyme, and season with 2 teaspoons salt. Let it simmer slowly for three hours.
Once the tongue is cooked, carefully transfer it to a pot of cold water and let it sit for about ten minutes. Use a small knife to peel off the tough outer skin.
Cut the peeled tongue into thin slices and serve.
Plum butter sauce
In a skillet, heat 1 Tablespoon unsalted butter over medium-high heat. Add 1 Tablespoon all-purpose flour and stir until the mixture starts to foam.
Reduce the heat, add 1 cup plum butter and lukewarm ½ cup beef broth, and stir. Season with ¼ teaspoon cinnamon, 1 teaspoon lemon peel, and ½ teaspoon salt. Simmer gently for 10 minutes.
Finally, add 1 Tablespoon spiced rum. If the sauce is too thick, thin it out with a little broth. If the plum butter was not sweet enough, add sugar, and adjust salt to taste.
Notes
The basic recipe makes about 6 portions.
SERVING: Serve warm. Place the plum sauce on the plate and arrange slices of cooked tongue in it. Add two to three slices of bread dumplings.
Expect to have some leftover cooked beef tongue. The tongue is usually sold whole as one piece, not portioned out.