Wash onion, carrot, potato, and celery thoroughly, then cut into bite-sized pieces.
Add olive oil to a pot and sauté the onion over medium heat.
Add the remaining vegetables and sauté together.
Pour in water or vegetable stock and bring to a boil.
Season with bay leaves, salt, and pepper.
Simmer until the vegetables become tender.
Remove the bay leaves and serve the finished soup in a bowl.