Mary Berry Meat and Potato Pie with Dauphinoise Potatoes and Steak

Name: Mary Berry Meat and Potato Pie with Dauphinoise Potatoes and Steak
Prep time: 20 min
Cook time: 2 h 40 min
Total time: 3 h
Cuisine: British
Ingredients: 1 kg (2½ lb) stewing steak, cubed; 1 tbsp sunflower oil; 2 large onions (chopped); 350 g (12 oz) small open (dark-gilled) mushrooms, sliced; 2 tbsp heaped plain flour; 600 ml (1 pint) beef stock; 1 tbsp Worcestershire sauce; Salt and black pepper (to taste); A little gravy browning (optional); 1.1 kg (2½ lb) potatoes, peeled; 50 g (2 oz) melted butter; 50 g (2 oz) grated Cheddar