Peel potatoes and rinse with cool water.
Cut the potatoes in quarters or smaller if they are large potatoes. Add them to a large kettle/saucepan. Cover the potatoes with cold water and add salt.
Cook potatoes over medium-high heat uncovered just until the start to boil. Reduce heat to medium, cover, and cook until the potatoes for about another 15 minutes. Time will vary with the size of the potato. Test with a fork for doneness.
Once the potatoes are tender remove from the heat and drain the water completely.
Add the milk, sour cream, Parmesan cheese, garlic powder, and onion powder. With a potato masher or an electric mixer process, the potatoes until they are mashed and fluffy.
Transfer to a serving bowl and serve immediately.