Put the chickpeas in a large bowl and add plenty of water (they will double in size so add more water if necessary). Soak them overnight.
The next day drain and rinse the chickpeas, then measure out 2.5 cups and put these into your food processor.
Roughly chop the onion, garlic, parsley and add these to the chickpeas. Then add the chickpea flour, cumin, ground coriander, salt & pepper, cayenne and cardamom or turmeric. (If your food processor is small, toss everything a large bowl first, then divide the mixture into two-three portions before processing).
Turn on the food processor and pulse until you get a coarse but sticky texture, resembling fine couscous. You’ll need to scrape the mixture down the sides of the processor occasionally.
When you’re happy with the consistency (it should stick together) transfer it to a mixing bowl. Do the same with the other batches.
Add the flax egg or egg (if used) and combine the mixture with a fork.
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 bicarb if you like. Mix well. Using a Tbsp (or small ice-cream scoop), add a dollop into your hand and shape balls or patties with your hands. The size of the balls/patties is up to you - I like golf ball sized ones. If the mixture is not binding well, then add some more chickpea flour to it.
Put the falafels on a plate. You should get between 15-20 falafels from the mixture.
Fill a small saucepan with vegetable oil to a depth of 3cm or so. Heat the oil over medium heat then test with some crumbs. If it’s sizzling - then you’re ready to go.
Carefully put 5-6 falafels in the oil and fry for 2-3 minutes, then turn them 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.