For the Salisbury Steak:

• 1 pound ground beef, 90% lean
• 1/2 onion, finely diced
• 2 garlic cloves, minced
• 1/3 cup panko bread crumbs
• 1 large egg
• 1 1/2 teaspoons Worcestershire sauce
• 2 teaspoons mayonnaise
• 1 teaspoon sea salt
• 1/2 teaspoon black pepper
• 1 1/2 teaspoons Italian seasoning
• 1 tablespoon ketchup
• 1 1/2 teaspoons milk
• 2 teaspoons Dijon mustard
• 1 tablespoon olive oil, for sautéing

For the Mushroom Gravy:

• 1/2 yellow onion, finely diced
• 1 tablespoon unsalted butter
• 8 ounces brown mushrooms, sliced
• 2 garlic cloves, minced
• 2 tablespoons all-purpose flour
• 1 1/2 cups beef broth
• 1/2 cup water
• 1/2 teaspoon Worcestershire sauce
• 1/2 teaspoon Dijon mustard
• 2 teaspoons ketchup
• 1/4 teaspoon sea salt
• 1/8 teaspoon ground black pepper