Spray slow cooker generously with spray oil. Combine all ingredients except the pecans/walnuts into slow cooker and stir to combine.
Cover and cook on low for 2-3 hours or until liquid is absorbed and apples are soft. If you want to cook overnight, add an extra 1/3 - 1/2 cup of milk, cover and set to "Keep Warm" setting. Add an extra splash of milk or cream if a bit dry when ready.
Before serving, stir in chopped nuts of choice and serve with an optional drizzle or honey or maple.
If your slow cooker doesn't have a "Keep Warm" setting, I suggest putting it to low and only cooking no more than 4 hours--maybe cook at night before bed and chill until breakfast.