Heat oil in a large saucepan; add bacon and cook, stirring occasionally, until crisp. Remove from pan.
Add leeks to pan and cook, stirring for about 5 minutes or until leeks are tender. Add potatoes and stock and bring to the boil; reduce heat and simmer, uncovered, for about 40 minutes.
Remove from heat; cool slightly. Using the StickMaster, process until thick and chunky.
Add cooked bacon to soup and reheat until hot. Season to taste with freshly ground pepper.