Add the onion, celery, carrot and garlic cloves to a large saucepan and spray with low calorie cooking spray. Gently fry over a medium heat for 10 minutes, until softened.
Add the tinned tomatoes, butter beans, cauliflower, basil, balsamic vinegar, stock and Henderson's Relish to the saucepan. Reduce the heat and simmer for 40 minutes with a lid on the pan, stirring occasionally.
When ready, blend the soup until smooth. If you need to add extra water at this point you can do so. Season with salt and pepper to taste.
Whilst the soup is simmering, slice each of the bread rolls into 3 slices down the middle. Cut each slice into cubes.
Add the bread cubes to a frying pan. Coat with low calorie cooking spray and sprinkle over garlic granules. Toast over a medium heat for 5 minutes, until the bread is crispy.
Serve the soup with some croutons sprinkled on top.