Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Place the chickpeas, spinach, parsley, garlic, hemp hearts, cumin, coriander, salt, and pepper into a food processor and pulse until the mixture is coarsely ground.
Pour in the liquid egg whites and pulse a few more times until the mixture is well-combined and holds together when pressed, but is not a smooth paste.
Using your hands, form the mixture into 8 small, thick patties and arrange them evenly on the prepared baking sheet.
Bake for 20 to 25 minutes, flipping the patties halfway through, until they are firm and the outsides are golden and crisp.
While the falafel is baking, prepare the drizzle by whisking together the Greek yogurt, tahini, lemon juice, and lemon zest in a small bowl until smooth.
Serve the hot falafel warm, topped generously with the lemon-tahini drizzle.