Melt butter and oil in a large pot over medium heat.
Sauté celery and onions until tender.
Add flour and cook for 30 seconds, stirring constantly.
Add chicken stock, potatoes, corn, sugar, salt, white pepper, and red pepper flakes.
Cover and simmer until potatoes are tender, about 30 minutes.
Add milk and simmer until soup has thickened to a creamy consistency, about 15 minutes.
Garnish with cheese, chopped parsley, and chopped bacon and serve warm.