Peel the radish and cut into small pieces, do the same with the onion.
Melt the butter in a saucepan and sauté the onions briefly. Add the radish and stir occasionally. After a few minutes add the vegetable stock. Let the soup simmer for 20 minutes with the lid closed. In the meantime, puree the pre-cooked beetroot.
When the cooking time is up, add the beaker of sour cream. If you like, you can add some cream cheese. The soup is only seasoned with salt and pepper, as the radish already has a great flavor.
Just before serving, add some cold beetroot to the center of each serving.
The earthy taste makes the radish a little bit spicy and also tastes good to people who otherwise don`t eat beetroot. If you stir your soup, you get the perfect pink soup, but it is also sweeter in taste.