Add dry chickpeas to a large bowl that will allow room for expansion. Cover with plenty of water so that the chickpeas will still be fully immersed when they soften and expand. Soak the chickpeas overnight.
When they're ready, drain chickpeas and add to a food processor. Depending on your food processor's capacity, you might have to do this in two or three batches.
Pulse until the garbanzo beans are ground, then transfer to a large bowl.
Add the onion, garlic, parsley, cilantro, and serrano to the food processor and pulse until finely ground.
Add the herb mixture to the garbanzo beans and mix until thoroughly combined.
Mix the spices and add to the garbanzo and herb mix, followed by the flour. Knead with your hands until all the ingredients are combined.
Test to see if the mixture holds together by pressing 1 tablespoon of the mixture into a small disc or ball. You may need to run it through the food processor one more time if it's too coarse.
If the mixture still does not hold together, add additional flour, one tablespoon a time until it does.
Fry one falafel in 375-degree F oil until brown and crisp on both sides. This should take approximately one to two minutes. Drain on paper towels.
Taste the falafel to see if any adjustments need to be made to the seasoning.
If no adjustments are necessary, form the remaining falafel. Fry as many as you will be serving and freeze the rest for another time. See the notes below for freezing instructions.
Serve hot with flatbread or pita bread, Middle Eastern Salad, and Tahini Sauce.