2.Boil, steam or microwave potato until tender, drain. Mash potato in large bowl until smooth, cool.
3.Whisk egg whites in small bowl until frothy, add to potato with crab, onion, parsley and flour. Shape mixture into eight patties, place on tray. Cover, refrigerate 10 minutes.
4.Meanwhile, preheat oven to 220°C (200°C fan-forced).
5.Make tzatziki. Coarsely grate cucumbers squeeze out excess moisture. Place in large bowl with garlic, juice and yogurt, stir to combine.
6.Coat patties in breadcrumbs, spray with a little oil, return to tray. Bake about 30 minutes or until browned lightly. Serve with tzatziki.