Clean your potatoes with a stiff-bristled brush and cold water. After you've thoroughly cleaned the potatoes, look them over and remove any bruises or mis-colored spots.
Using a fork, work your way around each potato stabbing deeply into it's flesh. 6-12 stabs should do it depending on the size of the potatoes you are using. This allows steam to escape during the cooking process.
Dry the potatoes off with a paper towel and preheat the oven to 350°F. Take a small bowl and add just a splash of your chosen oil, and have a container ready for the potatoes once they've been oiled. Then lightly salt and pepper each one and put aside as you wait for the oven to heat up.
Once the oven has heated, arrange the potatoes directly on the cooking rack and place a baking sheet on the rack underneath them to catch any drippings.
Cooking time will vary from 1 hour and up depending on the size and quantity of potatoes you cook. The skin should be puffed up, golden-brown and crispy, and the potato should squish easily and be very soft on the inside.
When the potatoes have about 30-35 minutes of cooking left, heat a medium skillet to medium-high heat. Add 2 teaspoon of butter and 1 teaspoon of extra-virgin olive oil and let the butter melt. Add the onions and saute them until they are soft and translucent (about 5-7 minutes). Add the peppers and cook with the onions for about 8 minutes or until peppers are crisp-tender. Add the smoked sausage, reduce heat to medium-low, cover and let cook, stirring occasionally.
Once the potatoes have been properly cooked, carefully remove from the oven. Keep in mind that potatoes retain heat for quite a while, so use tongs or an insulated cooking mitt to remove the potatoes.
Cut the potatoes open and fluff with a fork. Add butter, additional salt and pepper (if desired). Top the potatoes with the smoked sausage mixture. Top with Italian cheese, if desired. Place on a microwavable plate and microwave in intervals of 30 seconds until the cheese has melted.