Ingredients: Freshly ground black pepper,1-1/2 tablespoons butter, softened,2 English muffins, separated into halves,3 teaspoons garlic, very finely chopped, divided,2 teaspoons prepared horseradish (optional),1 lb lean ground beef (we used grass-fed),1 tablespoon mayonnaise,8 ounces mushrooms, sliced,1 medium onion, sliced and separated into rings,1 tablespoon panko crumbs,1/2 teaspoon salt,4 slices Swiss cheese,1 tablespoon vegetable oil
Course: lunch,main course,main dish,dinner
Cuisine: American