Preheat the grill to high. Put the diced chicken breast in a food processor and whizz until finely chopped. Add the onion, garlic and parsley and whizz again until finely chopped, pushing the mixture down the sides of the bowl occasionally.
Divide the mixture into small patties – you should be able to make about 40. Grill for 10 minutes, turning halfway through, until the patties are completely cooked through.
Meanwhile, make the tzatziki. In a small bowl, mix together the cucumber, garlic, yogurt and mint sauce.
Serve the chicken patties with the tzatziki, vegetable sticks and pitta bread.