Rinse the chickpeas under cold water and discard any bad ones. Place in a large saucepan and cover with water. Let soak 24 hours then rinse again.
Place the chickpeas, onion and potato in the bowl of a food processor. Cover and process until finely chopped.
Leaving about 1 cup of the chickpea mixture in the food processor bowl pour the rest into a mixing bowl.
Add the garlic, coriander, coriander, cumin, salt, pepper and cayenne pepper to the chickpea mixture in the food processor bowl; process on low to blend thoroughly. Return the reserved garbanzo bean mixture to the food processor bowl and add the lemon juice and olive oil. Process on low until it looks like coarse crumbs.
Cover and refrigerate for 2 hours.
Stir the bicarbonate of soda into the chickpea mixture until evenly blended. Using damp hands form the mixture into 4cm diameter balls.
Pour the canola oil into a wok 3 to 5cm deep and heat over medium-high heat.
Cook the falafel balls turning so all sides are evenly browned; about 5 minutes. Remove falafel from oil and drain on paper towels.
Repeat to cook remaining falafel balls.
If you don't have time to soak the dry chickpeas for this recipe, substitute with three 400g tins of chickpeas and start at Step 2.