Pat the pork chops dry with kitchen roll. Sprinkle salt and pepper all over them. Heat the olive oil in a large skillet, frying pan or casserole over a medium to high heat. Stir in the butter. As soon as the butter has melted, add the pork chops to the pan and sear them, about 2 to 3 minutes on each side. Reduce the heat slightly if the chops brown too quickly.
Remove the pork chops from the pan and pour off most of the fat. Add the shallots or onions and cook them on medium to high heat until softened, about 1 minute. Add 120ml of the wine and bring to a boil, deglazing the pan by scraping the brown bits from the bottom of the pan.
Stir in the stock and return the chops to the pan. Bring the sauce to a simmer, reduce the heat, cover and cook until the chops are cooked through (63C internal temperature – I check with my Thermapen), about 10 to 15 minutes.
Remove the pork chops to a warm platter and cover with foil to keep warm. Add the remaining 120ml of wine. Increase the heat to high to boil the pan juices. Reduce the juices by half, about 3 minutes.
Remove from the heat and add the double cream, stir to mix well and then return to the heat and boil for 3 minutes more, until sauce reduces and thickens, and scraping the pan with a wooden spoon leaves a trail.
Remove from the heat and whisk in the mustard and parsley. If you want, add more mustard to taste. Place the chops on the bed of sauce and serve with sides of your choice.