Soak the shank in cold water for 1 hour, drain it, and put it in a large saucepan with the bouquet garni, 1 minced onion, 1 clove of degermed garlic, crushed, the coarse pepper.
Leave to cook uncovered and in small broth for 90 minutes.
On the other hand, put the lentils in a saucepan, cover generously with water, add 1 minced onion, 1 clove of garlic, degermed, crushed and chopped, leave to cook over medium heat for 30 minutes,
Until only two tablespoons of liquid remain, add the butter in chunks. Adjust the seasoning.
Put in a large dish (square salad bowl), place the shank preserved in its cooking.
If however the lentils are too dry, you can add a little cooking juice from the hock.