1. Start by caramelizing the onions. In a medium skillet, melt the butter over medium heat. Add the thinly sliced onions and cook, stirring occasionally, until they’re golden brown and caramelized, about 15-20 minutes. Set aside.
2. While the onions are caramelizing, prepare the ‘secret sauce’ by mixing mayonnaise, ketchup, Dijon mustard, and pickle relish in a small bowl. Adjust the seasoning to taste and refrigerate until ready to use.
3. Preheat a grill or stovetop griddle over medium-high heat.
4. Divide the ground beef into four equal portions and shape them into thin patties. Season each patty with salt, pepper, and Worcestershire sauce.
5. Cook the patties on the preheated grill or griddle. Cook for about 3-4 minutes on each side, or until cooked to your desired doneness. Set aside and keep warm.
6. To assemble the patty melts, spread a small amount of the secret sauce on each slice of low-carb bread.
7. Place one slice of Swiss cheese and one slice of cheddar cheese on four slices of bread.
8. Top each with a beef patty, followed by a generous portion of caramelized onions.
9. Place another slice of low-carb bread on top, completing the sandwich.
10. Heat olive oil in a large skillet over medium heat. Grill each sandwich for about 2-3 minutes per side, or until the bread is crispy and the cheese is melted.
11. Serve immediately and enjoy your low-carb patty melt with additional secret sauce on the side.
Variations & Tips
For a spicier version, add a few slices of jalapeño or a dash of hot sauce to the secret sauce. For those who prefer a different type of cheese, feel free to substitute with your favorites like provolone or pepper jack. If you’re avoiding bread altogether, try using large portobello mushroom caps or lettuce wraps as a low-carb alternative.