Peanut or other neutrally flavored oil, for frying
To cook the chickpeas: Drain the chickpeas from the soaking water and place in a medium saucepan. Toss in the garlic, bay leaf, carrot, celery, thyme and onion. Add water to the pan until it covers the chickpeas by about 2 inches of water.
Put the pan on a high heat and bring the water to a boil, reduce to a simmer and simmer until the chickpeas are very soft and tender, 35 to 40 minutes. Turn the heat off.
Season the water generously with salt and let sit for 15 minutes. Drain the chickpeas from the cooking liquid and remove the veggies, bay leaf and thyme and discard.
To make the falafel: In a food processor, pulse the chickpeas until they look coarse and grainy but are NOT a puree.
In a dry saute pan, toast the coriander and cumin seeds over medium heat until they are very aromatic, 3 to 4 minutes. Pulverize in a spice grinder until they are a powder.
Transfer the pulsed chickpeas to a mixing bowl and add the cilantro, parsley, breadcrumbs, cayenne, garlic, lemon zest, onions and ground spices. Gently stir to combine. Taste the mixture to see if the mix needs seasoning, season with salt if needed.
Form the mixture into balls the size of walnuts and gently press to make patties. Lightly dust with flour on both sides and pat off excess. Place the patties on a sheet tray and let hang out in the fridge for at least 1 hour.
Add oil to a large straight-sided saute pan until the oil is about 1/2-inch deep. Bring the oil to a medium-high heat. Add the falafel to the pan and fry them on both sides until they are brown and crispy.
Remove the falafel from the pan and dry on paper towels.
Serve the falafel in pitas with lettuce, tomatoes, cucumbers and Tahini Sauce.
In the food processor, combine the tahini, lemon juice, cilantro, garlic and cayenne. Puree until smooth. While the machine is running, add the olive oil and about 1/2 cup water. Season the sauce with salt. Taste and re-season, if needed. Refrigerate, covered, until ready to serve.