Simple Salisbury Steak W/ Brown Gravy

INGREDIENTS

• 1 -1 1/2 lb ground beef (I used very lean)
• 1/2 cup crumbs-saltine bread, Ritz crackers, panko, seasoned stuffing mix
• 1 egg, lightly beaten
• 1 1/4 ounces onion soup mix, Lipton's divided
• 1/2 teaspoon black pepper
• 1/2 teaspoon salt, completely adjustable per your tastes
• 1 small yellow onion, finely diced
• 10 ounces heinz beef gravy, jar
• 2 tablespoons butter or 2 tablespoons olive oil
• 2/3 cup water
• 2 -4 teaspoons Worcestershire sauce
• 2 -4 teaspoons ketchup or 2 -4 teaspoons tomato sauce
• 1/2 teaspoon mustard powder
• 1/2 cup mushroom, sliced