1. Begin by gently mixing the ground beef with the garlic powder, onion powder, Worcestershire sauce, salt, and pepper until the seasonings are evenly distributed. Be careful not to overwork the meat, as this can result in tough patties. Divide the seasoned beef into four equal portions and shape them into patties, making a slight indentation in the center of each one.

2. In a skillet, melt the butter and add a splash of olive oil over medium heat. Add the sliced mushrooms and thinly sliced onions, then sauté for 3-4 minutes, or until the vegetables have softened and begun to caramelize. Season with salt and pepper to taste. Remove the sautéed mushrooms and onions from the pan and set them aside.

3. In the same skillet, heat the remaining olive oil over medium-high heat. Add the seasoned beef patties and cook for 4-5 minutes per side, or until they reach your desired level of doneness. During the last minute of cooking, top each patty with a slice of Swiss cheese and allow it to melt.

4. While the patties are cooking, spread a thin layer of butter on one side of each slice of bread. Heat a separate skillet or griddle over medium heat and add the buttered bread, toasting it for 2-3 minutes per side, or until it’s golden brown and crispy.

5. Place one of the toasted bread slices, buttered side down, on a clean surface. Top it with a cooked beef patty, followed by a generous portion of the sautéed mushrooms and onions. Place the second slice of toasted bread, buttered side up, on top to complete the sandwich.

6. Return the assembled Mushroom Swiss Patty Melt to the skillet or griddle and cook for 2-3 minutes per side, pressing down gently with a spatula to help the cheese and fillings meld together. Once both sides are golden brown and the cheese is melted, your Mushroom Swiss Patty Melt is ready to serve!