In a large saucepan, heat milk over medium heat until bubbles form around side of saucepan. Remove from the heat. Add the soup, cream cheese, garlic, nutmeg and pepper; stir until smooth.
Place the potatoes and onion in a 3-qt. slow cooker. Pour the milk mixture over the potato mixture; mix well. Cover and cook on low for 6-7 hours or until potatoes are tender. Sprinkle with paprika if desired.