French Lentils with Sausage, Wilted Arugula, & Dijon Mustard Recipe

Heat oil in a large, straight-sided pan that has a lid until oil shimmers, then add sausage. Stir sausage to brown for several minutes, cooking until fat has rendered out and sausage is very crispy. Reduce heat if sausage looks like it will burn. While sausage is browning, trim 1/8 to 1/4 inch from the root and blossom ends of onion (leaving enough so onion leaves will stay intact), then slice in half. Remove skin and stud onion with cloves. Add to pan with lentils, bay leaves, and 4 1/2 cups water. Bring mixture to a boil, then reduce to a simmer and cover. Cook until lentils are tender but still have a bite, about 45 minutes. After half an hour of cooking, add a pinch of salt to season lentils (reserving some to add at end). When lentils are done, turn off heat and fold in mustard and arugula until arugula just wilts. Salt to taste and serve.