To prepare the chicken patties: in a bowl, combine all the ingredients together. Mix well until combined then wrap the mixture and refrigerate for an hour. Preheat the grill on medium heat.
Form into 4 patties and grill for 8 minutes per side. To prepare the burgers: spread mayonnaise and ketchup on the bottom half of the burger buns. Top with chicken patties, lettuce, cucumber, onion and finally with the bun. Press lightly.
Serve immediately