Peel carrots, onions and potatoes. Cut carrots and celery into small cubes. Cut the potatoes into equal pieces.
Chop one onion. Prick the other onion with cloves. This is called a "oignon cloûté". Chop the garlic.
Heat a little olive oil in a casserole dish. Sauté the chopped onion for 2 to 3 minutes. Add the carrots, celery and potatoes and fry for 5 minutes.
Season with smoked paprika, some black pepper and salt. Deglaze with the broth. Pour in the lentils and add thyme, rosemary and onion studded with cloves. You can add dark soy sauce to flavor the stew and make it darker.
Simmer over medium heat for 30 to 40 minutes.
Wash the spinach and chop it coarsely. Once the lentils are cooked and shortly before serving, remove the thyme, rosemary and "oignon cloûté". Add the spinach. Mix well and cook for 5 minutes.