In a medium pot add sweet potatoes and cover with salted water. Bring to a boil, lower the heat and simmer until fork tender, 15 to 18 minutes.
Season chops with salt and pepper. Heat 1 tablespoon extra-virgin olive oil, a turn of the pan, in a large skillet over medium-high heat. Cook pork 5 minutes on the first side until deeply golden, turn and cook 3 to 4 minutes more with a loose foil tent over the pan. Remove cooked chops to a plate and cover to keep warm. Add another turn of the pan of olive oil, add the onions and apples. Season with salt, pepper and thyme and cook until just tender, 5 to 6 minutes. Douse with juice of a lemon and remove onions and apples to a bowl; keep warm.
Add 2 tablespoons butter to the skillet, melt then whisk in flour, cook 1 minute then whisk in cider and 1 cup of stock. Season the gravy with salt and pepper. Thicken 4 to 5 minutes over medium-low heat.
Drain cooked sweet potatoes and return pan to stove. Melt 2 tablespoons butter and combine with marmalade and 1 cup stock. Add potatoes and mash, season with salt and pepper.
Serve chop covered with apples and onions, gravy poured down over top, sweet potatoes alongside.