Tongue with Vinegar

Simmer the vegetable broth and cook the tongue in it for 3 hours. Peel the tongue while it is still warm, then brown it for a few seconds in a saucepan with butter. Deglaze with red wine vinegar. Add salt and pepper. Add vegetable broth and reduce for 3 to 5 minutes. Add a dash of Dijon mustard to the tongue and serve.