(A day in advance) Place the dried chickpeas and baking soda in a large bowl filled with filtered water to cover the chickpeas by at least 5cm/2in. Let it soak in the fridge for at least 12 hours (if the chickpeas are still too hard after 12 hours, leave it for up to 24 hours). When ready, drain the chickpeas completely and dry them.
Place the chickpeas, herbs, onion, garlic, salt and spices in the food processor.
Run the food processor for 2 to 3 minutes on high-speed, scraping down the sides as needed until everything is well incorporated, forming a falafel batter. (The falafel batter should look smooth.)
Transfer to a bowl and add flour and baking powder. Mix well.
Refrigerate for 30 minutes.
Scoop +/- tablespoon of the falafel batter into balls (or discs) and place on a tray. It should yield about 15 falafels. (If you find the batter too wet, add another tablespoon of chickpea flour. If it's too dry and crumbly, add a teaspoon or two of water.)
Pour the oil into a skillet or large pot. Heat to medium-high temperature (between 180-190°C/350-375℉) until gently bubbling.
Place the falafel balls with a large spoon and slide them gently, being careful not to burn yourself. Cook in batches (avoiding crowding the falafels in the pan) for about 4 minutes, until browned and crispy on the outside. Use 2 forks to flip the falafels half way of cooking.
Remove the falafels from the oil and drain them on paper towels. Repeat with remaining falafels.
Serve warm with your choice of dipping sauce or make a sandwich with falafel balls on pita bread with arugula, tomato, and cucumber. Pour some tahini sauce or hummus on top. Enjoy!