Add cut potatoes to the pot and add water to cover. Bring to a boil and cook for 12 minutes or until fork tender.
Drain and return potatoes to the pot. Add the sour cream, butter, chiles, salt, and pepper. Mash with the potato masher until smooth. Add more salt and pepper to taste. Serve warm.
TIPS: These can be made ahead. Place mashed potato mixture into greased 2 quart baking dish and keep in the refrigerator for up to two days. Bring to room temperature, then top with 1 tablespoon of butter cut into small pieces. Bake uncovered at 350° F for 35 minutes.