Arrange a rack in the middle of the oven and heat to 400°F.

Heat the oil in a large cast iron skillet or oven-safe frying pan over medium-high heat until very hot and almost smoking. Meanwhile, pat the pork chops dry with paper towels. Generously season all over with salt and pepper. Add the pork to the pan and sear undisturbed until golden-brown on the bottom, 4 to 5 minutes. Transfer to a large plate.

Reduce the heat to medium, add the onion and thyme, season with salt, and cook, stirring occasionally, until tender, about 4 minutes.

Add the wine, scrape up any browned bits at the bottom of the pan with a wooden spoon, and cook until almost evaporated, 3 to 4 minutes. Stir in the cider or juice and whole-grain mustard and bring to a simmer. Return the pork browned-side up, and add any juices accumulated on the plate to the pan.

Roast until the pork registers 145°F on an instant-read thermometer inserted into the thickest part of each chop, 6 to 12 minutes depending on the thickness of the chops. Transfer the pork chops to serving plates.

Place the pan over medium-high heat, whisk the smooth Dijon mustard into the sauce, and simmer until reduced slightly, about 2 minutes. Remove from the heat and whisk in the cream. Taste and season the sauce with salt and pepper as needed. Serve the sauce with the pork chops.