Heat oven to 180C/fan 160C/ gas 4. Heat half the oil in a frying pan and cook the onions for
5 mins until they are soft and just starting to turn golden. Remove and set aside. Pour the remaining oil into the pan and fry the black pudding for about 1 min on each side. Remove, drain on kitchen paper
and set aside.
Cook the chops in the pan on a high heat so you get a good colour on the outside, but they’re not cooked, then drain off the fat. Set the chops aside.
Layer the ingredients in a deep ovenproof casserole, which holds everything snugly, starting with some potatoes and carrots and dotting half the mustard over each layer of black pudding. Season as you build up the layers and sprinkle the herbs throughout. You should have two layers of chops and finish with overlapping potato slices.
Pour the hot stock over everything, then brush the top with the melted butter. Cover and bake for 2 hrs, until everything is meltingly tender, removing the lid for the last half hour to crisp up the potatoes.