Welsh Lamb and butter bean stew

Ingredients

• 2 boneless PGI Welsh Lamb neck fillets or 2 leg steaks, cut into chunks
• 1 tbsp oil
• 1 onion, chopped
• 2 sticks celery, finely chopped
• 2 carrots, sliced
• 2 garlic cloves, crushed
• 1 tbsp tomato purée
• Seasoning
• Sprigs of thyme and rosemary
• 450ml lamb or veg stock
• 150g bag baby spinach, shredded kale or cavolo nero
• 400g tin butter beans, drained and rinsed
• Thyme leaves or mint to garnish