Set a saucepan over low heat and add the olive oil. Add the squash and celery root and season with sea salt. Cover the pot with the lid and let the vegetables cook until tender, about 30 minutes, stirring from time to time. The vegetables are usually done when all the natural juices have evaporated.

In another saucepan, bring the chicken stock to a boil. Using an immersion or standing blender, blend the vegetables with the hot stock, adding just enough stock to achieve rich, creamy soup.

Pour this mixture into a clean saucepan and bring to a simmer over medium heat. Whisk in the butter, season with salt and a dash or two of Tabasco, to taste.