Mary Berry's shepherd's pie recipe

Ingredients

• 750 g minced lamb
• 125 g mushrooms, sliced
• 2 carrots, diced
• 1 large onion, chopped
• 1 garlic clove, crushed
• 30 g plain flour
• 150 ml beef stock
• 2 tbsp Worcestershire sauce
• 1 pinch salt and black pepper
• 750 g potatoes
• 4 tbsp hot milk
• 30 g butter