Lancashire hot pot

1) Preheat the oven to 180C/350F/Gas 4.
2) Heat the oil in a pan and fry the lamb pieces until brown all over. Remove and set aside
3) Repeat with the kidneys, remove and mix with the lamb pieces.
4) Add the onions to the pan adding more oil if necessary and cook for 2-3 minutes.
5) Add the flour and stir, cook for 2 minutes more.
6) Add the stock, thyme, bay leaves and Worcestershire sauce. Bring to the boil then turn down to a simmer and cook for 10 minutes.
7) Grease a flame-proof casserole dish, place a layer of potatoes (about a third) over the bottom of the dish and season.
8) Top with a layer of lamb and kidneys, then lay over half of the black pudding slices.
9) Pour over half of the stock.
10) Repeat this process until all of the ingredients are used, finishing with a layer of potatoes.
11) Dot the top layer of potatoes with the butter.
12) Place the casserole into the oven to cook for 20 minutes.
13) Remove the lid and cook for a further 20 minutes, or until the potatoes are golden-brown.