Dissolve the stock cubes in the boiling water.
Add all the remaining ingredients to the slow cooker and pour in the stock.
Mix well then cook for 4-5 hours on high.
When all the veg is cooked and the barley is tender, remove a couple of ladles of veg and stock then blitz it in a food processor until it's smooth.
Add this back into the soup and stir. This will thicken it slightly.
Leave it to cook for another 10-15 minutes. Stir in the chopped parsley and serve