Combine chick peas, juice of 1 lemon, oregano and parsley in food processor. Mash garlic into paste with some salt pressing under the flat part of your knife then add garlic to processor along with tahini paste. Process hummus, drizzling in olive oil, until smooth then transfer to a bowl and stir in olives, reserving a few for garnish. Serve dip with pita crisps and vegetable sticks.