Par-Cook the Chickpeas: Drain the soaked chickpeas, transfer them to a large pot, and cover with several inches of fresh water. Bring to a vigorous boil and cook for 10 minutes. This step helps soften their skins for a creamier final texture. Drain the chickpeas thoroughly and set aside.
Roast the Aromatic Core: Preheat your oven to 200∘C (400∘F). Slice the top quarter-inch off the head of garlic to expose the cloves. Place it on the foil on the baking sheet, drizzle with 1 tablespoon of the olive oil, and sprinkle with a pinch of sea salt. Wrap the garlic in the foil and roast for 30-35 minutes, until the cloves are completely soft and fragrant. Set aside to cool slightly.
Build the Vegetable Foundation: While the garlic roasts, heat the remaining 3 tablespoons of olive oil in your Dutch oven over medium heat. Add the chopped onion and leek, cooking for 7-8 minutes until softened and translucent. Add the diced carrots and celery and continue to sauté for another 5 minutes to build sweetness.
Simmer the Soup: Add the par-cooked chickpeas and the low-sodium vegetable broth to the pot. Season with the ¾ teaspoon sea salt, black pepper, dried oregano, and smoked paprika. Stir everything to combine, bring the soup to a gentle simmer, then reduce the heat to low, cover, and cook for 60-75 minutes, or until the chickpeas are perfectly tender.
Create the Silken Emulsion: Once cool enough to handle, squeeze the soft, roasted garlic cloves out of their skins. Ladle about 3 cups of the soup (including chickpeas and vegetables) into your blender. Add the roasted garlic cloves and the tahini. Blend on high speed until completely smooth and creamy. (Safety Note: If using a standard blender, ensure you vent the lid to allow steam to escape.)
Finish and Fortify: Pour the blended purée back into the pot with the remaining soup and stir until fully incorporated. Place the pot back over medium-low heat. Stir in the fresh lemon juice, baby spinach, chopped dill, and chopped parsley. Cook for just 2-3 minutes more, until the spinach is fully wilted. Taste and adjust seasoning if necessary.
Serve and Garnish: Ladle the hot soup into bowls. Garnish each serving with a generous drizzle of high-quality extra virgin olive oil, a sprinkle of fresh dill, and serve immediately with a fresh lemon wedge on the side.