Heat the butter and oil in a saucepan over a medium heat until the butter has almost melted, then and fry the onions, celery, carrot and bacon lardons until onions have softened but not browned.
Add the chicken stock, oatmeal, nutmeg and herbs.
Bring to the boil and then cover and gently simmer for 15 minutes.
Add the potato and simmer for a another 15 minutes or until the potato is cooked, but still firm.
Serve into soup bowls and top with grated cheddar cheese and enjoy with with some crusty bread.