Mushroom Swiss Burger

Instructions

1. Prepare the burger patties
   In a large bowl, gently combine the ground beef, Worcestershire sauce, garlic powder, onion powder, salt, and pepper. Do not overwork the meat. Divide the mixture into 4 equal portions and form into patties about 1/2-inch thick and slightly wider than your buns, as they will shrink when cooking. Use your thumb to make a slight indentation in the center of each patty to prevent bulging during cooking.
2. Sauté the mushrooms
   Heat a large skillet over medium-high heat. Add the butter and when melted, add the sliced mushrooms and onions. Cook without stirring for 2-3 minutes to allow browning, then stir and continue cooking for another 5-7 minutes until the mushrooms have released their moisture and begin to caramelize. Add the minced garlic and thyme, and cook for an additional 1 minute until fragrant. Season with salt and pepper to taste. Remove from heat and set aside.
3. Cook the burgers
   Preheat a grill or large cast-iron skillet to medium-high heat. If using a skillet, add a thin layer of oil. Cook the patties for 4-5 minutes on the first side. Flip and cook for an additional 3-4 minutes for medium doneness (160°F internal temperature). During the last minute of cooking, place 2 slices of Swiss cheese on each patty and cover to allow the cheese to melt completely.
4. Prepare the buns
   While the burgers are cooking, lightly toast the brioche buns, either on the grill or in a toaster. Spread the Dijon-mayonnaise mixture on both the top and bottom halves of each bun.
5. Assemble the burgers
   Place each cheese-topped patty on a bottom bun. Top generously with the sautéed mushroom and onion mixture. Add the top bun and serve immediately while hot. If desired, secure with a toothpick to hold the burger together.