"After having one of these burgers at a local catering place, I had to adapt my own version! These are extremely filling and taste great with chipotle mayonnaise and sliced cheese! These may be refrigerated or frozen for later use."
Bring beef broth to a strong boil in a saucepan over high heat. Stir in quinoa; reduce heat to low and cover. Cook until broth is absorbed, about 15 minutes. Remove from heat; let stand for 5 minutes. Fluff with a fork; let cool.
Chop spinach in a food processor; transfer to a bowl. Chop onion, Parmesan cheese, and garlic in the food processor; add to the spinach. Mix in cooled quinoa, bread crumbs, salt, red pepper flakes, garlic powder, and black pepper. Add egg whites and egg; stir burger mixture to combine.
Shape burger mixture into 4 equal patties. Heat a skillet over medium-high heat and coat with cooking spray. Cook patties until cooked throughout, 4 to 6 minutes per side. Serve on hamburger buns.