Preheat oven to 350 °F. Pierce potatoes with a fork, then rub with butter and sprinkle with salt. Place each potato into an individual baking dish and bake for about an hour, until they yield when gently pressed. While baking, prepare gravy.
To make the gravy
Add butter and flour to a small saucepot over medium heat. Stir constantly with a wooden spoon until a rich brown, the color of peanut butter (this takes 7 to 10 minutes). Slowly pour in stock in a thin stream, whisking constantly, then stir in thyme. Bring to a simmer, season to taste and keep warm.
Cut an oval opening into top of each potato (you can reserve these for another use, such as Smoked Salmon Potato Skins). Scoop out most of the potato and mash with butter, and season lightly. Spoon mashed potato back into their skins. Ladle gravy into each potato and top with cheese curd. Return potato to oven to melt cheese, about 10 minutes, then serve immediately.