Heat the oil over a medium heat in a large saucepan. Add the chopped onion and potatoes, season well, then reduce the heat and cover the pan.
Gently cook for about 10 mins until starting to soften, then add the stock bring to the boil. Add the cabbage, cut in stripes.
Simmer for 10 mins more.
Blend he soup in the food processor until smooth and leave a few potatoes in the pan.
Pour the soup in bowls, season to taste, add the remaining potatoes and serve with a sprinkle of grated Leicester cheese.