Place potatoes in a large pot with enough water so potatoes are entirely covered. Bring water to a boil. You can check if they are ready if potato can be pierced with a fork. Remove potatoes from salted water. Reserve salt water.
In a large bowl, add potatoes, sour cream, and 1/4 cup reserved salt water. Fold in butter while mashing potatoes. (Add more reserved water to reach desired creaminess of potatoes.) Mash until everything is evenly mixed. Season with salt and pepper then mix in ranch packet. Garnish with chopped chives on top.