In a medium pot (3-quart/3-liter is perfect), heat the oil. Add minced onion, diced celery and diced carrot. Sauté on medium-high for 10 minutes, stirring from time to time.
Next, add minced garlic and stir for about a minute or until it releases its aroma.
Pour in 1 cup of water and add the rest of the ingredients: cooked lentils, crushed tomatoes, salt, pepper and dried basil. Stir well. Bring to a boil and simmer (reduce the heat to medium)until the carrots and celery are cooked through, about 25 minutes (see note 3).
