Dice the celery and carrots into small pieces.
Heat 74ml olive oil in a heavy-bottomed pan and add the celery and carrots.
Peel and dice the onion to the same size as the other vegetables and add to the pan.
Dice the potatoes to the same size and add them to the pan.
Add the unpeeled, crushed garlic and sweat vegetables for a few minutes to color slightly.
Add bouquet garni, 2 litres of water, salt, and pepper, then simmer for 10-15 minutes.
Combine basil leaves and chopped parmesan in a bowl for the pistou.
Add 100ml olive oil, season, and blend until smooth using a hand blender.
Add drained beans to the soup and remove the bouquet garni.
Continue cooking until all vegetables are tender and beans are heated.
Ladle into bowls, swirl in pistou, drizzle with oil, and serve with bread.