Place a medium, heavy-based pan over a gentle heat. Add the olive oil and when it’s hot add the beetroot, celery, garlic and onion. Season with salt and pepper and cook, stirring regularly, for 12–15 minutes, or until the vegetables are beginning to soften and smell sweet and tasty.
Meanwhile, peel, quarter and core the apples, then slice them thickly. When the vegetables are ready, add the apples to the pan, stir, then cook for a further one to two minutes before adding 600ml of water. Place a lid on the pan and bring the soup to the simmer. Leave to simmer gently for 10 minutes, until all the vegetables are tender.
Ladle the soup into a blender. Add the apple juice and whiz until smooth. Return the soup to the pan and bring it briefly back to the simmer. Season with salt and pepper to taste and remove from the heat.
If you intend to serve the soup cold, leave it to cool, then transfer it to a bowl. Cover and place in the fridge to chill for three to four hours.
You can serve the soup just as it is, but I like to finish it with a swirl of olive oil, a scattering of fresh basil, a spoonful of organic natural yoghurt, and even a small, whole baked apple, but that’s entirely optional.