Peel and wash potatoes and cut into large chunks, roughly 2 inches. Try to keep the size somewhat uniform.
Lightly spray a 6- or 7-quart crockpot with nonstick spray. Place potatoes inside. Add broth, optional garlic, and salt; stir. Cover and cook on Low for 5 to 6 hours or High for 3 to 4 hours, stirring once during cooking time.
When potatoes are fork tender, don’t drain them. Add butter, sour cream, and milk. Mash using a potato masher. For whipped potatoes, use a hand mixer. Add more milk as needed to achieve desired consistency. Taste and season with salt and pepper, as needed.
Leave the mashed potatoes in the slow cooker on warm until ready to serve.
Video
Notes
Brown Butter Option: When potatoes are nearly done cooking, brown butter in a small pan over medium heat. Hint: Use a light color pan so you can see the color of the butter. Keep cooking, swirling or stirring to prevent burning. Once the melted butter is golden brown in color and smells nutty, remove the pan from heat. Pour the butter into a bowl so it stops cooking and doesn't scorch, or add it directly to the potatoes before mashing.
Optional Add-Ins (stir into potatoes after they are mashed): fresh chopped parsley and/or chives); shredded Parmesan or cheddar cheese.
Cooking note: When we tested this recipe, potatoes were fully cooked in 3 hours on High.