Brown the chorizo cut into small pieces with the finely chopped onion in the casserole without adding fat. Add the sliced carrots and lentils and cover with the chicken stock.
Add the bouquet garni, the cloves pricked in a quarter of the onion, salt, pepper and a touch of Espelette pepper. Cover and simmer over low heat for 40 to 45 minutes, monitoring regularly and stirring occasionally.
Meanwhile, steam the potatoes.
In a saucepan, cook the Morteau sausage for 20 minutes in simmering water without piercing its skin.
Dress and serve immediately