Ingredients:
2 pounds (about 4–5 medium) russet or Yukon gold potatoes
4 tablespoons unsalted butter (more to taste)
½ cup milk (or half-and-half for creamier mash)
¼ cup sour cream (optional for extra tang and creaminess)
Salt and freshly ground black pepper, to taste
Optional: chopped chives, garlic, shredded cheese, or cream cheese
Instructions: