Combine potatoes, salt and enough water to cover in a large pot over medium heat. Boil for 20 minutes or until potatoes are soft enough to mash. Drain, return potatoes to the pot and mash with a potato masher. 

While potatoes cook, combine butter and milk in a small saucepan over low heat.  Stir until butter melts completely. Add butter/milk mixture to potatoes and stir.  Add sour cream, season with salt and pepper. Place warm mashed potatoes in a serving dish, top with pats of butter and a sprinkle of chives. Serve.