Season chops with salt and pepper. Heat oil in a skillet over medium-high heat and brown chops for 2 minutes per side in 2 batches, then transfer to a 6-quart slow cooker.
Cook mushrooms in the same skillet for 8 to 10 minutes until their liquid evaporates and edges brown. Add shallot for 1 minute, then wine and scrape the pan; simmer for 2 minutes.
Pour mushroom mixture over chops with broth and rosemary. Cover and cook on low for 6 hours, checking at 5 hours, until fork-tender and at least 145°F, usually closer to 190°F for this marbled cut.
Lift pork carefully to a platter and rest for at least 3 minutes. Transfer mushrooms and cooking liquid to a saucepan, skim excess fat and bring to a simmer.
Mix cornstarch with cold water, stir into the simmering liquid and cook for 2 minutes until lightly thickened. Spoon mushrooms and gravy over the chops.