Drain and rinse chickpeas. Coarsely mash with the back of a fork or potato masher.
Combine chickpea liquid, parsley, onion, garlic, lemon juice, spices and tahini in the bowl of a food processor and process into a paste.
Stir purée and baking soda into mashed chickpeas. Add in breadcrumbs, 1/2 cup at a time, stirring well after each addition, until mixture holds its shape when pressed in the palm of your hand.
Preheat oven to 375°F.
Scoop falafel mixture out into desired portion sizes. (I usually make each falafel the size of a golf ball.) Spread out on a lined baking tray. Optional: brush or spray lightly with olive oil to help them stay more moist as they crisp in the oven.
Bake for 45-50 minutes, rotating pan halfway through to ensure evening cooking. (Or, air fry for 20 minutes at 450°F.)