To prepare the chickpea soup, start by soaking the chickpeas in water for about 8 hours or overnight.
After soaking, drain and rinse the chickpeas thoroughly.
Trim the leek by removing the base and tough outer leaves, then slice it into thin rounds.
Peel and finely chop the carrot.
Trim the base of the celery stalk and finely chop it.
Peel and finely chop the white onion.
In a large pot or Dutch oven, heat a little olive oil, add the chopped vegetables and a ladle of water, then let them sweat gently over low heat for 10 minutes.
Add the chickpeas along with the rosemary and bay leaves tied together with kitchen twine, then cover with water.
Pour in the tomato purée, cover with a lid, and cook for 2 and a half hours. Season with salt near the end of cooking.
Remove the herb bundle, then taste and adjust the salt and pepper as needed. Scoop out a ladle of chickpeas with some of the cooking liquid and blend with an immersion blender until smooth and creamy.
Pour the blended cream back into the pot and stir well to combine. Serve the chickpea soup warm, finished with a drizzle of extra virgin olive oil, freshly ground black pepper, and fresh thyme leaves.