Wash the sweet potato and prick it all over with a fork. Wrap in a clean, damp dishtowel and microwave on high for 5 minutes. CAREFULLY check it by squeezing it - you may need to use another dry dishtowel to do this - the potato will be hot. It should give a bit when squeezed, so if it stills seems hard microwave on high for another 2 to 3 minutes. Let cool until you are able to handle it with bare hands. Scoop the flesh out of the sweet potato and discard the skin.
In a food processor, combine chickpeas, sweet potato, green onions, parsley, cayenne pepper, garlic powder, cumin, salt and pepper, flour, and one tablespoon oil, 1/4 cup of the barley and 1/4 cup of the quinoa. Process until the mixture is a cohesive paste.
Put the chickpea/ sweet potato mixture in a large bowl and mix together with the remaining barley and quinoa. I find it is easiest to do this with my hands.
Form the mixture into 6 patties.
You can cook these right away in a frying pan lightly greased with olive oil; or you can place them on greased wax paper and freeze for later.