Preheat oven to 350°F. Prick potatoes with a fork and rub with oil. Roast until just tender but not fully cooked. Let cool then cut them through lengthwise. Gently scoop out potato centers and spray shells/skins with a little oil. Season the inside of potatoes with salt and pepper, and broil to brown the flesh a bit.
For the filling, heat a large skillet over medium-high heat with a turn of the pan of oil. Add sliced dogs and brown and crisp, 2 minutes. Remove to a plate, add another turn of oil to the pan and add beef. Brown and crumble the meat, and season with salt, pepper, chili powder, cumin, coriander and allspice; stir a minute to toast spices. Add onions and garlic to chili, and stir to soften 3-5 minutes. Add tomato paste, stir, then Worcestershire and stock. Slide dogs back into chili and simmer a few minutes to thicken a bit.
Fill potato skins with chili, top with cheese and broil to melt cheese. Top with a fat drizzle of Gulden’s spicy brown mustard and chopped white onions to serve.