Wash the potatoes. Pat them dry and coat with a thin layer of oil. Preheat the oven to 350 degrees. Place the potatoes on the middle rack in the oven. Bake for 50 - 60 minutes or until very tender when pierced with a fork. Pressure Cooker Method: Place the potatoes on the steamer rack in the cooker. Add 1 1/2 cups of water. Cover and make sure the vent is turned to closed. Press the Lentil/Beans button and the Time Adjust button for a total of 10 minutes. When the potatoes are done, place them on a plate. Cut the potatoes down the center but, not all the way through. Carefully, squeeze both ends of the potato while pressing towards the center. This allows the middle to blossom out. Place 1 tablespoon of butter on each potato, salt, and pepper to taste. Serve hot with your favorite toppings.