Wash the lentils and add them to the pan with the onions and 5 parts water. Add the bouquet garni and cook for 20 minutes.
In a heavy-bottomed saucepan, brown the minced onion.
In the meantime, fry the cleaned and halved button mushrooms. Add them after 20 minutes of cooking the lentils. Make a round trip for the chorizo slices and put them with the lentils. Continue cooking for another 20 minutes.
When the lentils are almost done, cook the lamb.
Serve the lentils, mushrooms and chorizo in a soup plate, then add 1 skewer per person.
In a frying pan with a little oil, cook the brochettes over high heat for 3 to 4 minutes on one side and 5 minutes on the other, with sage, salt and pepper.