How to Make It
Heat 1 tablespoon olive oil in a large saucepan over medium. Add onion and garlic; cook, stirring often, until tender, about 4 minutes. Add vegetable stock, 1 3/4 cups water, and 1 teaspoon salt; bring to a simmer. Set aside 1 cup chickpeas; add remaining chickpeas to stock mixture. Cover and reduce heat to medium-low; simmer 10 minutes.
Meanwhile, heat 1 tablespoon oil in a small skillet over medium-high. Add reserved 1 cup chickpeas; cook, stirring occasionally, until toasted and browned, 8 to 10 minutes. Stir in cumin and remaining 1/8 teaspoon salt.
Pour stock mixture into a blender. Remove center piece of blender lid (to allow steam to escape); secure lid on blender, and place a clean towel over opening in lid. Process until smooth. Add tahini and lemon juice; process until smooth. Ladle soup into 6 bowls; drizzle with remaining 2 tablespoons oil, and sprinkle with cheese and toasted chickpeas.