Once your potatoes are cooked through (a knife easily glides into them), begin the prep for your mash. Gently heat the milk and butter in a wide pot until the butter has melted. If you have a potato ricer, use it to process your potatoes directly into the pan. If you are using a potato masher, place your boiled potatoes in the pan and mash. You want to be left with a creamy mix that is free from lumps. Season with salt to taste.