Chef John's Salisbury Steak

Details

Ingredients

• 1 pound 85% lean ground beef
• ½ teaspoon freshly ground black pepper
• 1 teaspoon dry mustard
• 2 tablespoons ketchup
• 1 tablespoon Worcestershire sauce
• 1 teaspoon soy sauce
• 1 large egg, beaten
• 1 pinch cayenne pepper, or to taste
• ½ cup plain bread crumbs
• 2 tablespoons salted butter
• 12 large white button mushrooms, sliced
• 1 cup diced onion
• 1 pinch salt
• 2 tablespoons all-purpose flour
• 2 tablespoons ketchup
• 1 tablespoon Worcestershire sauce
• 3 cups high-quality, low-sodium beef broth
• salt to taste
• 2 tablespoons salted butter