Place the chickpeas in a large bowl and cover with a couple inches of water. Cover the bowl and refrigerate for 12 to 24 hours.
Drain the chickpeas in a colander then add them to a food processor along with the shallot, garlic, parsley, cilantro, baking powder, coriander, cumin, salt, and pepper. Process into a smooth paste, scraping down the sides of the food processor bowl as necessary. Transfer the mixture to a bowl and refrigerate for at least 2 hours.
Brush 2 TBSP of the oil onto a rimmed baking sheet. Place the oiled baking sheet in the oven while it preheats to 400°F.
Take the chickpea mixture out of the refrigerator and set aside a large plate. Take a heaping tablespoon-size of the mixture and form it into a ball then press down to form into a disk roughly 1/2-inch thick. Place the falafel disc on the plate and continue to make more discs with the rest of the mixture.
Take the baking sheet out of the oven and carefully place the falafel disks on the baking sheet using a spatula. Brush the tops of the falafel discs with the remaining 2 TBSP of oil.
Bake in the oven for 12 minutes then carefully flip them over and bake 12 more minutes or until browned on both sides.
Stir together the tahini sauce ingredients. If necessary add a little bit of extra cold water at a time until desired consistency.