Heat olive oil in a saucepan over a medium heat.
Add chopped onion and celery.
Cook until vegetables start to golden.
Sprinkle the flour over the vegetables and stir through.
Pour in the milk, add the sweet potato and bring to a boil.
Make sure to stir to stop the soup sticking to the pot.
Cook until the potatoes are tender.
Add the corn and chopped spring onions.
Bring the soup back to the boil, then serve.
Sprinkle some chopped chives or parsley on top for some added flavour.