In a medium bowl, cover the chickpeas and fava beans with cool water by several inches. Soak them overnight and up to 24 hours.
Drain the chickpeas and fava beans. In the food processor, process them with a teaspoon of salt until they are ground to a coarse crumb. Add the mint, parsley, cilantro, jalepneo, garlic, onion, and sesame seeds and pulse until everything is finely ground and the mixture is a fine, web crumb—but not pureed. Transfer the mixture to a bowl, stir in the baking soda, and chill for at least 30 minutes and up to one day.
Make the tahini sauce:
To make the tahini sauce, in a small bowl, stir the tahini, salt, and garlic until combined. Add the lemon juice and stir, then slowly add the water, working through the sludgy phase until the sauce is smooth. Taste and adjust with salt, lemon juice, or water if needed. Set aside.
Make the falafel waffles:
Preheat the waffle iron according to the manufacturer's instructions. You can lightly grease it to prevent sticking. A nonstick waffle iron helps a lot!
Scoop enough of the falafel mixture into the preheated waffle iron to thickly coat the waffle grooves, spreading it evenly. Close the lid and cook until the waffles are crisp and golden brown, usually about 5-7 minutes.
Carefully remove the falafel waffles from the iron. Repeat making waffles with the remaining falafel mixture. Serve them immediately, while they are still hot and crisp, with the tahini sauce drizzled over the top and on the side for dipping.