Wash the sweet potatoes, pierce with a fork, and microwave on your microwave potato setting or bake at 400 for 40-45 minutes. Let cool slightly then rinse under cold water to speed up the cooling. Can place in fridge for several minutes to speed up the process.
Meanwhile, whisk together the ground flax seed and water in a small bowl. Refrigerate for at least 15 minutes. Whisk again. It should form a paste--this is your flax "egg."
While sweet potatoes are cooling, chop onion and garlic. Sauté onion in olive oil over medium-high heat for about 5 minutes until softened and translucent. Add garlic and cook for another 2 minutes or so. Remove and set aside.
Combine quinoa and 1/2 c. water in a small pot. Bring to boil and let simmer for 15 minutes (give or take) until the liquid is absorbed. Set aside.
Chop red pepper. Thaw frozen spinach in the microwave. Drain thoroughly. Rinse garbanzo beans and mash with a fork in a separate bowl until mushed together. Some pieces of bean remaining are ok.
Scrape the flesh from the sweet potatoes into a large mixing bowl. Mash with a spoon or masher until smooth. To sweet potatoes, add onion and garlic, red pepper, spinach, quinoa, and garbanzo beans. Mix to combine. Add in "flax egg" and stir. Shape mixture into patties (I did about 10 small patties--make them however large or small you desire) and place on a wax paper-lined baking sheet. Place in fridge for at least 30 minutes.
Once chilled, heat a little bit of olive oil in a large frying pan over medium heat. Once hot, place burgers in pan and cook for about 2-3 minutes each side or about 5-7 minutes total. Let them get a little charred on the outside to add to the flavor. Serve on buns, english muffins, rice, salad, or whatever suits your veggie burger fancy. Enjoy!