The Mushroom Monster

• 12 portobello mushroom, gills scraped clean and diced (reserve the bodies for another dish)
• 1 1/2 tablespoons dried thyme 
• 1 teaspoon black pepper
• 1 teaspoon granulated garlic
• 1 teaspoon salt 
• 1/2 teaspoon mustard powder 
• 2 cups ground beef
• 1 teaspoon Worcestershire sauce 
• 1 tablespoon butter
• 4 slices fontina cheese
• 8 slices cooked bacon
• 4 slices red onion
• 4 leaves lettuce
• 4 slices tomato
• 1/4 cup ketchup 
• 1/4 cup mayonnaise
• 4 gourmet buns

Prepare the mushrooms: heat a dry nonstick skillet over medium heat. Add the diced mushroom gills and cook until all of the moisture has cooked out and the mushrooms are very dry, about 10 to 15 minutes. Let cool. 

Make the spice blend: mix together the dried thyme, black pepper, granulated garlic, salt, and mustard powder.

Once the mushrooms have cooled, add them to a large bowl with the ground beef and Worcestershire sauce and mix to combine. Form into 4 patties about 1/2-inch thick. Season the patties generously with the spice blend. 
 
Heat a cast-iron skillet over high heat until hot. Lower the heat to medium, add the butter and cook the burgers until they are seared on one side, about 3 minutes. Flip the patties and cook until they’re seared on the other side and register 170°F (medium) on a meat thermometer, about 3 minutes. In the last minute, add a piece of sliced fontina to each burger and let melt.

Arrange the burgers on the buns, add the cooked bacon (2 slices per burger), lettuce, onion, tomato, ketchup, and mayo. Top with the over half of the bun and enjoy.