Golden veggie shepherd’s pie

INGREDIENTS

• 50g butter
• 2 onions , chopped
• 4 carrots , diced
• 1 head of celery , chopped
• 4 garlic cloves , finely chopped
• 200g pack chestnut mushrooms , sliced
• 2 bay leaves
• 1 tbsp dried thyme
• 500g pack dried green lentils (we used Merchant Gourmet Puy lentils)
• 100ml red wine (optional)
• 1.7l vegetable stock
• 3 tbsp tomato purée
• 2kg floury potatoes , such as King Edwards
• 85g butter
• 100ml milk
• 50g cheddar , grated