Preheat grill or cast iron skillet med-high heat.
In a small bowl marinade onions with A-Premium Balsamic Vinegar – let sit for at least an hour. Onions will turn purple/red.
In a bowl combine ground beef, ground turkey, garlic, kosher salt, and pepper. Form into 12 small patties. Set aside.
In a small bowl combine goat cheese and mayonnaise until smooth. Set aside.
Grill the patties until golden and cooked through, about 3 minutes per side.
Toast the buns on grill for 15 seconds.
Spread the tops of the bun with the goat cheese mixture, add cooked patties, onions, avocado and spinach. (optional – sauté onions, add tomatoes)