Soak chickpeas overnight in cold water. Drain and combine with water in a pan, simmer for about 40 minutes. Drain in a colander and rinse under cold water. Puree with an immersion blender. Peel garlic and grind finely with salt. Add to chickpeas and mix with tahini, lemon juice, cumin powder, season with salt to taste and refrigerate, covered, for 30 minutes.
Rinse parsley, shake dry and pluck off leaves. Place hummus into bowls and make small wells with a spoon. Fill wells with olive oil and garnish with olives, lemon wedges and parsley leaves. Serve with fresh sesame pita bread.