Heat the oil in a large saucepan. Add the onion and cook on a medium heat for 3-4 minutes, stirring occasionally until the onions softens.
Add the chopped corned beef and stir into the onions (no need to cook it through). Sprinkle on the three beef stock cubes, then add in the water. Stir and bring to the boil.
Add in the carrots and potatoes and simmer for 10 minutes. Stir a few times to break up the corned beef.
Stir in the cauliflower, cider vinegar, salt and pepper, then simmer for a further 10 minutes, stirring a couple of times during cooking.
Mix the cornflour with the cold water in a small bowl to make a slurry. Stir a little of the slurry at a time into the soup, until the soup thickens to your liking.
Taste the soup and season further if required, then divide between four bowls. Top with parsley before serving for a dash of colour.
Tastes amazing with some pickled red cabbage or beetroot slices!!