Wash the tongue well and boil it. Strain the broth and put the cleaned and chopped vegetables in it to boil as well. Salt.
Peel the boiled tongue and cut it into thin slices. Separately, prepare a sauce from the warmed butter and toasted flour. Add the milk and mix again. Bring the sauce to a boil.
When serving, pour sauce over the slices and place vegetables on the sides, that you boiled with the tongue.