Heat the oil in a large skillet. Add the onion and the garlic and saute over medium-low heat for about 10 minutes.
While sauteing the onions and garlic, in a large pot, bring the broth to a boil. Add the lentils and the diced potatoes, wait until the liquid in the pot begins to boil again, turn the heat down to medium and cook for 10-15 minutes.
Meanwhile, add the ground chicken to the onions and garlic and cook over medium heat for 8-10 minutes, breaking up large clumps of chicken meat.
Transfer the onion, garlic and chicken mixture to the pot.
Add the tomato and stir. Then, add salt and pepper to taste.
Continue cooking over medium heat for another 10-15 minutes.
Serve hot, garnished with chopped fresh parsley or cilantro and slices of sourdough bread.