Lamb and red wine shepherd's pie with creamy kumara topping

Ingredients

• 500 g lamb mince
• 1/4 cup balsamic vinegar
• 1 onion, finely chopped
• 3 cloves garlic, crushed
• 1 large carrot, chopped
• 1/2 tbsp fresh rosemary, finely chopped
• a pinch of dried thyme
• 1 bay leaf
• 3/4 cup tomato paste
• 3 tbsp Worcestershire sauce
• salt and pepper
• 200 ml red wine
• 1 cup beef stock
• Kumara mash
• 1 kg kumara, peeled and steamed or boiled until tender
• 2 tbsp butter
• 1/2 cup milk