Peel and dice the vegetables into chunks of around 2cm or less. Add these to the slow cooker.
Add all of the remaining ingredients apart from the milk. Stir everything together.
Cook on high for 4 hours or low for 6 hours.
Check that the soup mixture is completely cooked through. The onions will be translucent and the vegetables can be easily sliced through with a knife. Then add the milk and cook for a further 15 minutes on high.
Next, carefully transfer the soup mixture to a jug blender and pulse until smooth. You can also do this with a stick blender directly in the slow cooker.
Serve immediately or allow to cool and store in the fridge or freezer.
Dice the vegetables into chunks no larger than 2cm to ensure that they are cooked through within the cooking time.
Blending The Soup
Once cooked, the soup will be hot. Take care when blending with a stick blender, or when transferring to a jug blender.
If required, the soup can be cooked for longer than four hours.Different brands and sizes of slow cookers operate at different temperatures. The stated cooking times should be used as a guide only.
This recipe makes a thick soup. If you prefer a thinner consistency, stir in milk or water in 100ml increments.