Shearers' Mince and Potato Hot Pot

Name: Shearers' Mince and Potato Hot Pot
Prep time: 35 min
Cook time: 45 min
Total time: 1 h 20 min
Cuisine: Australian
Ingredients: 5 medium potatoes, peeled and thinly sliced; 1 tablespoon olive oil; 1 pound ground beef; 1 onion, chopped; 1 tablespoon tomato sauce; 1 tablespoon Worcestershire sauce; salt and pepper to taste; 0.25 cup butter; 0.25 cup all-purpose flour; 2 cups milk; 1 cup shredded sharp Cheddar cheese; 1 (6 ounce) can mushrooms, drained; 2 tablespoons butter, diced