Place chickpeas in a large bowl and cover water. Soak overnight (12-24 hours). Choose a bowl large enough for them to triple in size and still be under water.
Drain chickpeas and add to food processor bowl with onion and garlic.
Process until roughly chopped (working in batches if needed).
Add parsley, cilantro, lemon juice, cumin, coriander, salt, pepper and cayenne. Process until well combined and green in colour.
Add chickpea flour and tahini. Process until evenly mixed.
Using a 1¼-inch portion scoop drop balls of dough onto a tray. Roll into balls with your hands or flatten slightly with a flipper to make small disks. Makes about 36 falafel balls.
Pan-fry, deep-fry or oven bake. Serve with tahini sauce. They freeze well.