Fry the onion and bacon in oil for 2-3 minutes. Stir in the potatoes, cauliflower and stock and bring to the boil. Cover and simmer for fifteen minutes or until tender. Liquidize the soup and then add milk. Reheat gently and season to taste. As an added touch, you can grill a couple of rashers of bacon until crisp; crush and sprinkle on top of the soup in the plate before serving.