Prepare the Mushroom Powder: Use a spice grinder or blender to grind dried mushrooms into a fine powder. In a large mixing bowl, combine the mushroom powder with ground beef, salt, black pepper, and Worcestershire sauce. Mix until well combined, then form the mixture into four equal patties. Make a small dimple in the center of each patty to ensure even cooking.

Cook the Toppings: In a skillet heat the olive oil over medium heat. Add the sliced mushrooms and onions, then cook them for 8–10 minutes until they soften and golden brown. Season with a pinch of salt, then set the mixture aside.

Grill the Burgers: Heat your grill or grill pan to high. Place the patties on the grill and cook them for 5–8 minutes per side, depending on your desire During the final minute of cooking, place a slice of Swiss cheese on each patty and allow it to melt.

Toast the Buns: Lightly coat the cut sides of the buns with olive oil. Place the buns on the grill, cut side down, and toast until golden brown, about 1–2 minutes.

Assemble the Burgers: Add the patty on the bottom half of each toasted bun. Top with the sautéed mushroom and onion mixture. Place the top bun on the patties and serve right away.