In the slow cooker, add in all your ingredients except for the milk and peanuts (for garnish).
Cook on low for 4 hours or high for 7-8 hours. If cooking on low, once in the last 2 hours, open the lid and give the ingredients a quick stir.
When done, blend until smooth (or to the consistency of your liking) with an immersion blender. Stir in milk until the soup is at the thickness you desire.
Serve with some toasted peanuts on top as garnish.
Notes
If cooking on low, avoid opening up the slow cooker more than once as you want to retain as much heat as possible in the short cook time.