Wash potatoes and put them in a large pot and cover with water. Bring to a boil and boil for about 30 minutes or until they are tender and a fork easily goes through. Pull potatoes out onto a cutting board and make a slit in the skin with a knife. Carefully use the side of a spoon to peel the skin off and put the inside of the potatoes into a large bowl. Add oil, salt and cinnamon and mash with a fork until they are the desired consistency. Add additional oil, salt or cinnamon as needed. How much depends on the potato. Sometimes, they are more moist and don't require as much oil. Salt and cinnamon is based on taste preferences.