You can easily use leftover ground beef and marinara sauce. I prefer a homemade sauce but jarred sauces work great here as well. Get our recipe for Simple Marinara Sauce here!
Cooking time assumes that the potato skin shells are already done. You can easily make the shells in advance, or use frozen ones from the french fry section of your grocery store.
You may need more or less beef and cheese based on exactly how large and deep the potatoes are, as well as how much you choose to fill them.