Heat the olive oil in a large pot over medium heat. Add the scallions, salt, and several grinds of pepper and cook for 2 minutes, or until softened but still bright green. Add 3 cups of the broth and 1 2/3 cups of the chickpeas and simmer, uncovered, for 15 minutes.

Combine the remaining 1 cup broth, the remaining 1 1/3 cups chickpeas, and the tahini in a blender and blend until creamy. Stir into the soup pot and simmer over low heat for 2 minutes.

Add the spinach, dill, and lemon juice and stir until the spinach is wilted. Season to taste with salt and pepper.

Portion into bowls and top with a generous swirl of olive oil, a squeeze of lemon juice, and a sprinkle of red pepper flakes. Serve with pita.