The easiest way to prepare mashed potatoes in the Crock-Pot or another slow cooker is to place peeled and cut potatoes in the slow cooker with liquid and cook until soft. To utilize typical local ingredients, consider buying the potatoes at a farmer's market.
Grease the liner of the slow cooker with butter. Peel 5 pounds of locally grown potatoes. Chop the potatoes into uniform 1-inch chunks.
Pour the potato chunks into the slow cooker. If desired, smash garlic cloves and place them on top. Season with salt and pepper to taste. Add 1 1/2 cups milk and stir. Cover, and cook on high for four to five hours. Scrape away any browned milk.
In a small saucepan, melt 1/2 cup unsalted butter over low heat. Add 2 cups of milk. For richer mashed potatoes, replace half the milk with cream. Warm gently. Remove the garlic from the potatoes, and use a potato masher to mash the potatoes. Stir in the milk. Use the slow cooker to keep the mashed potatoes warm until ready to serve.
As an alternative to cooking the potatoes in milk, replace it with 1 1/2 cups chicken broth. The mashed potatoes can also be seasoned with sour cream and chives in place of some of the milk during the mashing process.