1. In a medium bowl, combine the burger ingredients and form into patties. Place on a plate and refrigerate until ready to use.

2. In a small saucepan, melt the butter over medium heat. Add the onion slices and lower the heat to low.

3. Stir occasionally until the onions are caramelized.

4. In a small bowl, add the ingredients for the sauce and stir until combined. Refrigerate until ready to use.

5. Cook the bacon and break each slice in half. Set aside.

6. Place the burger patties on the grill or on a George Foreman and cook until desired doneness.

7. Toast the hamburger buns. Spread the sauce on both sides of the buns.

8. Top each burger with a slice of Swiss cheese and cook until melted.

9. Assemble the burger by placing the bacon, caramelized onions, tomato and spinach leaves on top of the burger. Serve with additional sauce for dipping.