Preheat oven to 400 degrees. Pierce sweet potatoes several times with a fork. Plack on a baking sheet and cook for 50 to 60 minutes, until tender. Allow to cool. Discard skin and mash.
If using flax egg, combine 1 tablespoon ground flax seed with 3 tablespoons warm water. Mix well and set aside.
In a food processor pulse 1 cup of the potato, chickpeas, quinoa, flour, pepitas, cilantro, onion, garlic, egg, Dijon, chile powder, cumin, paprika and salt until the mixture is chunky. (Do not over process.) Form into 6 patties and refrigerate for at least 1 hour.
Heat a grill pan or indoor grill to medium high and brush with oil. (You may also use and outdoor grill.) Cook for 10 minutes per side.
To make the sauce combine ingredients in a food processor and process until smooth.