In a food processor, pulse the chickpeas, onion, carrot, celery, garlic, and parsley until very finely chopped but not completely smooth. Add the flour, egg, spices and herbs, salt, and 2 1/4 teaspoons oil. Pulse until well mixed. Form into six patties. Cover and refrigerate overnight.
When ready to cook, heat the remaining 2 tablespoons oil in a large nonstick skillet over medium-high heat. Cook, turning once, until browned and heated through, about 8 minutes.
Sandwich in buns with sliced red onion and tzatziki.
These patties are best when you make them a day in advance. Whip up a batch now; tomorrow, just cook and devour.
Recipe by Josh Capon, executive chef and partner of B&B Winepub in New York City