Heat the vegetable oil in a large pot.
Add the chopped onion, garlic, carrots, and celery. Sauté until softened and fragrant.
Add the lentils, bay leaf, and vegetable stock. Bring to a boil.
Reduce the heat and let it simmer until the lentils are tender, about 15 to 20 minutes.
Finish with salt, pepper, and fresh parsley.
