My trick to making the lightest, crispiest falafel for stuffing into pita sandwiches? Soak dried chickpeas overnight before blitzing them in a food processor with the other ingredients. If you use canned chickpeas instead, your falafel will turn out dense and doughy - not what you want!
In a food processor, add the soaked and drained chickpeas and blitz until finely chopped. Scrape the sides and blitz again. Add ½ cup chopped onion, 2 cloves garlic, 2 tablespoons parsley, 1 tablespoon tahini, 1 teaspoon cumin, 1 teaspoon coriander, ¼ teaspoon kosher salt, and ⅛ teaspoon cayenne pepper. Cover and process, pulsing until the mixture is coarsely pureed. Add 2 tablespoons flour and ½ teaspoon baking soda, and pulse until blended.
Wet your hands, then form the mixture into 12 patties, about 1 ½ inches across. Chill the patties for 15-30 minutes.
Heat 1 inch of grapeseed oil to 350°F in a heavy-bottom skillet or Dutch oven over medium. Fry the patties in batches until golden, flipping halfway through, about 5 minutes. Drain on a paper towel-lined plate.
To make the sandwiches, open the halved pita and slather with a few dollops of tzatziki, then layer lettuce, cucumber, and tomato. Place 3 falafels in each pita half, top with sliced onion, and enjoy.