Prepare the Potatoes:
Peel the potatoes and cut them into evenly-sized chunks (about 1–2 inches). This ensures even cooking.
Boil the Potatoes:
Place the potatoes in a large pot and cover them with cold water. Add 1 teaspoon of salt.
Bring the water to a boil over medium-high heat, then reduce to a simmer. Cook for 15–20 minutes, or until the potatoes are fork-tender.
Drain and Dry:
Drain the potatoes in a colander and let them sit for 1–2 minutes to allow excess moisture to evaporate.
Mash the Potatoes:
Return the potatoes to the pot. Mash them with a potato masher or use an electric mixer for a smoother texture.
Add the Creaminess:
Stir in the butter, warm milk or cream, and sour cream (if using). Mix until smooth and creamy. Adjust the consistency by adding more milk if needed.
Season to Taste:
Season the mashed potatoes with salt and pepper to taste. Mix well to ensure even seasoning.
Serve:
Transfer the mashed potatoes to a serving dish. Garnish with fresh parsley or chives, if desired, and serve warm.