Pour water and chicken broth into a 4 - 6 quart slow cooker, then as you peel and cut each potato add them to the broth mixture in slow cooker to prevent browning.
Season with salt to taste.
Cover and cook on high heat 2 3/4 to 3 1/2 hours until potatoes are fully tender all the way through.
Drain potatoes in a colander in the sink. Then either return potatoes to slow cooker and mash with a potato masher, or for a completely lump-free option pass potatoes through a potato ricer or a food mill into slow cooker.
Add heated melted butter, heated half and half, season with more salt as needed then gently stir with a spatula or wooden spoon just to blend. Don't over-mix or they'll be gluey.
Serve warm, if desired topped with gravy or butter.
*Half and half amount can be adjusted depending on how thick or thin you like your mashed potatoes.