Scrub the potatoes. Peel if they have a thick skin.
Place the potatoes in the bottom of a large crockpot.
Add enough water to just cover the bottom.
Cook on HIGH 3 hours or LOW 6 hours.
If using peas or broccoli add them to the crockpot during last hour of cooking.
Mash potatoes with a potato masher or puree with an immersion blender.
Add milk, butter, salt and seasoning. Stir.
Serve immediately or keep the potatoes in the crockpot on warm for up to 4 hours.