Soak the chickpeas overnight. Drain and boil in fresh water till soft. Cool and remove the skin and put them in a food processor container. Add garlic, salt and tahina and blend. Add two tablespoons olive oil and blend. Add lemon juice and continue to blend till absolutely smooth. Transfer into a serving bowl and chill in the refrigerator. Just before serving drizzle the remaining olive oil. Sprinkle red chilli powder. Place two to three whole chickpeas on top and serve with pita bread.