Place the corn, vegetable stock, potatoes, onion, garlic, chillies, chilli powder, salt, parsley and black pepper in a slow cooker; cover. Cook on Low for 7 hours.
Pour the vegetable mixture into a blender filling the jug no more than halfway full. Hold the lid of the blender with a folded kitchen towel and carefully start the blender using a few quick pulses before leaving it on to puree. Puree in batches until smooth and pour into a clean pot. Alternately, you can use a stick blender and puree the mixture in the cooking pot.
Once everything has been pureed return it to the slow cooker. Stir the soy milk and margarine to the mixture; cook on Low for 1 hour more. Add the lime juice to serve.