1/2 pound French green lentils 1/4 cup good olive oil
2 cups chopped sweet onions
2 cups chopped leeks, white and light green parts only
1 teaspoon fresh thyme leaves
1 tablespoon minced fresh garlic
1 1/2 cups chopped celery (4 stalks)
1 1/2 cups chopped carrots (3 carrots)
1 1/2 cups homemade vegetable stock 2 tablespoons tomato paste
2 tablespoons good red wine vinegar (or more to taste)
Coarse salt and freshly ground black pepper to taste

Place the lentils in a heat-proof bowl and cover with boiling water. Set aside for 15 minutes, then drain.

Meanwhile, heat the oil in a sauté pan, add the onions, leeks, thyme, salt, and pepper and cook over medium heat for 10 minutes, until the onions are translucent. Add the garlic and cook for 2 more minutes. Add the celery, carrots, chicken stock, and tomato paste. Add the lentils; cover and simmer over low heat for 20 minutes, until the lentils are tender. Add the vinegar and season to taste.