If using raw beetroot, peel and chop it into roughly 1cm cubes.

Heat the olive oil in a large pot over medium heat. Add the onion and cook until softened, about 5 minutes.

Add the garlic and cook for another minute until fragrant.

Add the beetroot and apple to the pot. Pour in the vegetable stock and bring to a boil.

Reduce the heat and simmer for 30-40 minutes, or until the beetroot is tender.

Carefully blend the soup using an immersion blender or transfer to a regular blender. Blend until smooth.

Stir in the horseradish.

Heat the walnuts in a pan over a medium heat until browned slightly.

Pour the soup into bowls, put three tablespoons of yogurt on top of each bowl and pile the walnuts over the top.