Add the dried chickpeas to a large bowl. Cover by at least 2-3 inches with cold water. Soak overnight, then drain.
Add drained chickpeas, onions, garlic, parsley, cumin, coriander, salt, pepper and cayenne to the bowl of a food processor fitted with a steel blade. Process until the mixture is blended, but not pureed.
Sprinkle in the flour and pulse a few times. Add the mixture to a bowl and refrigerate, covered, for about 2-3 hours.
Remove mixture from refrigerator and form into walnut sized balls. If balls are not staying together, add a bit more flour. (I found 3 tablespoons of flour worked perfectly.)
Heat about 3 inches of canola oil in a deep pot to 375 degrees. Fry 4-6 balls at a time, a few minutes on each side (about 2 minutes each side), until lightly golden brown. Remove with a slotted spoon to a paper towel-lined plate.
Combine all ingredients in a medium bowl, whisk together until well combined. Chill.