Garlic roast lamb with hotpot potatoes

Name: Garlic roast lamb with hotpot potatoes
Ingredients: 1.8kg part-boned leg of lamb; 5 garlic clove, sliced; a few rosemary sprigs; a few thyme sprigs, plus a few extra to serve; 50g butter; 2 large onion, thinly sliced; 400g pack diced mutton or lamb shoulder, finely choppped; 2kg large potato, such as King Edwards, thinly sliced; 300g carrot, sliced at an angle; 3 tbsp plain flour; 700ml lamb or beef stock, plus 450ml (optional); 2 tbsp Worcestershire sauce; steamed green beans and wilted spinach with nutmeg (optional), to serve