Preheat the oven to 400ºF if making the roasted chickpea topping.
For a smoother hummus: Simmer 2 ½ cups canned chickpeas for 15 minutes to soften. Drain and rinse. (Or use soft-cooked chickpeas.)
For the roasted chickpeas: Meanwhile, transfer the remaining ½ cup chickpeas to a baking dish. Toss with olive oil and garlic powder and bake at 400ºF until crispy.
Transfer the 2 ½ cups cooked chickpeas to the canister of a blender with the tahini, garlic, lemon juice, turmeric, black pepper, long pepper powder (if using), and 3 tablespoons cold water plus one ice cube.
Blend until smooth, adding more cold water until the desired texture. Add maple syrup to taste to balance the spices.
For serving: Top with the roasted chickpeas and freshly ground black cumin seeds.