Soak the chickpeas. Add the chickpeas into a large bowl and cover with water. (The chickpeas will double or triple in volume, so use more water than you think you will need). Soak the chickpeas for 24 hours at room temperature. Then drain the chickpeas, rinse under cold running water, and use as instructed.
Preheat the air fryer. Set the air fryer temperature to 370°F/187°C and let the air fryer heat for 3-5 minutes.
Process all the ingredients. Add the soaked chickpeas, parsley, cilantro, onion, garlic, chickpea flour, cumin, coriander, black pepper, and salt into a food processor with an S blade and process until well combined. The texture of the chickpeas should be uneven and coarse, with some slightly larger pieces still visible. The mixture should hold together when you press it between your fingers, but it shouldn't be completely puréed. If the mixture is too wet, add a little bit more chickpea flour, 1 Tbsp./5.7 g at a time. If it's too dry and crumbly, pulse it a little bit more.
Season. Taste and adjust the flavor as needed, adding more salt for saltiness, garlic for pungency, cumin for earthiness, coriander for a citrusy-nutty flavor, and cayenne pepper for heat.
Refrigerate the falafel mixture. Transfer the falafel mixture into a bowl, cover, and refrigerate for at least 30 minutes.
Form the falafel mixture into balls. Scoop out 1-2 tablespoons of the mixture and roll it gently between your hands into balls, 1.5 inch/3.8 cm in diameter. Avoid packing the balls too tightly or they will come out tough and dense. Repeat until all the falafel mixture is used up.
Air-fry. Arrange about 9 falafel balls in a single layer in an air fryer basket and air-fry until crispy and golden brown, for 13-15 minutes.
Serve immediately, while still warm and crispy over greens or in a warmed pita bread with hummus, tomatoes, and shredded lettuce.
Store. Leftover falafel keeps well in an airtight container in the refrigerator for up to 5 days, though best when fresh. For longer term storage, freeze uncooked pre-shaped falafel in a single layer. Once firm, transfer the falafel into a freezer-safe bag or a container and place it back into the freezer for up to 3 months. (You can freeze cooked falafel as well, but it’s never quite as good).
Reheat in a 370ºF/187ºC air fryer until heated through and crispy again, for 3-4 minutes. If reheating frozen (uncooked) falafel, transfer the falafel into the refrigerator 24 hours before baking to thaw. Once thawed, follow the instructions for air frying above.