Prep Work: Chop mushrooms. Grind flax in small coffee bean grinder. Defrost meat if needed. (Remember to use fresh hamburger if making extra to freeze.) Combine meat with next 7 ingredients
Preheat oven to 400 degrees.
Combine all ingredients (except buns and garnishes listed afterward) in mixing bowl. Set aside and refrigerate half for the zucchini boats tomorrow or freeze in hamburger patties for later.
Grease roasting pan. Shape meat into balls and flatten; place on roasting pan.
Roast 6 min., then turn burgers over and roast 6-7 min. more.
Place buns cut side down on baking sheet and put in oven after flipping the patties. Begin checking after a few minutes and remove when toasted.
Build the hamburgers with mustard, mayo, ketchup, fresh tomatoes, avocado, provolone, spinach, etc. To eliminate carbs with protein, substitute buns with large pieces of leafy green lettuce wrapped around patties. Serve with fresh cut apple wedges for some fibrous, fresh crunch.