In a large pot, heat the olive oil over medium heat. Add the chopped onion, garlic, and a pinch of salt. Sauté for about 5 minutes until the onions are translucent and fragrant.
Add the diced carrots and celery to the pot and sauté for an additional 3-4 minutes, stirring frequently.
Stir in the cubed potato, cooked chickpeas, cumin, thyme, and bay leaf, mixing everything well.
Pour in the vegetable broth and bring the mixture to a boil. Once boiling, reduce the heat to low, cover the pot, and let it simmer for about 20 minutes or until the potatoes and vegetables are tender.
Remove the bay leaf, then use an immersion blender to partially blend the soup for a creamier texture while retaining some whole chickpeas and pieces of vegetables. Alternatively, transfer a portion to a blender, blend until smooth, then return it to the pot.
Stir in the lemon juice and zest, adjusting the seasoning with salt and pepper to taste. Let it simmer for another 5 minutes to meld the flavors.
Serve hot, garnished with freshly chopped parsley.