1. Wash and soak dry Chickpeas overnight in 6 cups of water (you may use 3.5 cups of water if using a pressure cooker).
2. Bring soaked chickpeas and water to a boil, reduce heat and cook until soft (cooking chickpeas may take about 90 minutes in a saucepan OR about 15 minutes in a pressure cooker). Once cooked, cool completely by placing in ice-cold water.
3. If using canned chickpeas, drain water, rinse with cold water and use. Blend together tahini, garlic, cold chickpeas, water/stock, lemon juice, salt and cumin powder until very smooth.
4. While the blender is still running add olive oil in a thin stream until the hummus is smooth and creamy. Garnish with sumac and drizzle a tablespoon of extra virgin olive oil.