Rinse the dried chickpeas and place them in a large bowl. Cover with plenty of water and soak overnight, or for at least 8 hours.
Drain and rinse the chickpeas after soaking. Pat them dry with a clean towel.
In a food processor, combine the soaked chickpeas, chopped onion, minced garlic, parsley, and cilantro. Process until finely ground but still slightly coarse.
Add the ground cumin, ground coriander, baking powder, cayenne pepper (if using), salt, and black pepper. Process again until the mixture is well combined.
Transfer the mixture to a bowl and gradually stir in the all-purpose flour until the mixture holds together and can be shaped into balls. The mixture should be slightly sticky but manageable.
Heat about 2 inches of vegetable oil in a large, heavy-bottomed pan or deep fryer to 350°F (175°C).
Using wet hands or a spoon, shape the falafel mixture into small balls or patties, about 1 to 1.5 inches in diameter.
Carefully drop the falafel into the hot oil, working in batches to avoid overcrowding the pan. Fry the falafel until golden brown and crispy on all sides, about 3-4 minutes per batch.
Remove the falafel from the oil and drain on paper towels.
Enjoy your meal!