Add oil and butter to a large saucepan over medium high heat. Add the bacon, onion and mushroom. Fry those for a good 5 minutes, then add the garlic powder, paprika, parsley, fennel, sage and black pepper. Fry for another 5 minutes.
Add the hot water and stock cubes to the pan and stir well. Bring to the boil then, simmer for 5 minutes. Soup will be ready.
If you wish to thicken the soup, add cornflour mixed with cold water at the very end and simmer till thickened.