Place 1 cup of dried chickpeas into a large glass bowl. Cover with cold water by at least 3 inches, as they swell dramatically. Let soak at room temperature for 18 to 24 hours. Drain completely in a colander and pat thoroughly dry with a clean kitchen towel. (Never use canned beans; they are already cooked and will turn into mush).

Add the soaked, dried chickpeas, flat-leaf parsley, cilantro, chopped onion, and garlic cloves to the bowl of a large food processor. Pulse in short 2-second bursts, stopping to scrape down the sides with a rubber spatula. Continue until the mixture is finely minced and resembles coarse wet sand or couscous. Do not blend into a smooth puree.

Transfer the green mixture into a mixing bowl. Sprinkle in ground cumin, ground coriander, sea salt, black pepper, and cayenne. Stir thoroughly with a wooden spoon until the spices are evenly distributed. Cover the bowl tightly with plastic wrap and refrigerate for 1 hour. Chilling allows the natural starch to hydrate and firm up so the patties hold their shape in hot oil.

Remove the chilled mixture from the refrigerator and sprinkle in the 1/2 teaspoon of baking powder, stirring well to combine. Using a 1.5-tablespoon cookie scoop or damp hands, press the mixture firmly into small balls or slightly flattened 1.5-inch round patties. Place them in a single layer on a parchment-lined baking sheet.

Pour 2 inches of neutral oil into a heavy cast iron Dutch oven and heat to 365°F (185°C). Carefully lower 5 to 6 falafels into the oil using a slotted spider strainer. Fry for 3 to 4 minutes, turning gently halfway through, until deep golden-brown and crunchy. Transfer to a wire cooling rack set over a baking sheet to drain. Repeat with remaining falafels. Serve immediately in warm pita with tahini.