Preheat the oven to 150C. Scrape all the meat off the lamb bone and put through a mincer with the carrot, celery, parsley, shallots and leftover gravy and fat from the roasting tin. If you haven’t got a mincer then chop everything finely and mix together.
Add sweet roasted garlic cloves popped from their skins (or fresh garlic) and the ketchup.
Press the mixture into an GN container. Mash together the cooked potatoes with butter to taste and a dash of milk, and top the meat with the potatoes. Use a fork to make a pretty design on top.
Cook in the oven for 30 minutes. Then turn up the oven to 200C for a final 10 minutes so it’s piping hot and lightly golden-brown on top.