Lightly coat the inside of a slow cooker with nonstick spray. Place potatoes, garlic, chicken broth, salt, and pepper into the slow cooker Cover and cook on low heat for 7-8 hours or high heat for 3-4 hours, or until tender.
Remove the potatoes and place in a large mixing bowl. Add the remaining ingredients and beat the potatoes on high until light and fluffy. If dry, add more milk as needed. Serve hot.