Soak the chickpeas in a large bowl of water overnight. The next day drain them, then measure out 2 cups and put these into your food processor.
Roughly chop the onion, garlic and coriander, then add these to the chickpeas. Then add the cumin, ground coriander, salt & pepper, cayenne or paprika. Pulse, until you get coarse, sticky mixture resembling couscous. (Depending on your food processor, you might have to do this in bathes)
Transfer the mixture to a bowl, add the seeds and enough chickpea flour for the mixture to be sticky and malleable.
Cover the bowl and chill for 1-2 hours.
When you’re ready to cook the falafels, take the mixture out of the fridge and add the baking powder. Mix well. Using a spoon (or small ice-cream scoop), shape balls or patties in your hands. If the mixture is not binding well, then add some more chickpea flour to it.
Coat the falafels in sesame seeds and put them on a plate. You should get between 15-20 falafels from the mixture.
Pour vegetable oil in a small, deep saucepan. Heat the oil over medium heat then test with some crumbs. If it’s sizzling - then you’re ready to go.
Carefully put about 5 falafels in the oil and fry them for 2-3 minutes, then turn over and fry until golden brown all over. Using a slotted spoon, transfer them to a plate, lined with kitchen paper towels.
Remove any fried crumbs from the oil with the slotted spoon and repeat the above with the remaining falafels. You might need to add more oil.
Serve the falafels with your favourite condiments.