In a large dutch oven cook bacon until browned. Reserve 1 1/2 tablespoons of pan drippings. Set bacon aside.
Add onion to the dutch oven with the reserved bacon drippings. Cook until softened, about 5 minutes. Sprinkle with 2 tablespoons of flour. Cook 2 minutes.
Pour clam juice and water over the top. Add potatoes, celery, bay leaf, kosher salt and cajun seasoning. Bring to a boil. Reduce heat and cook until potatoes are fork tender.
Stir 3 tablespoons of hot broth into the milk to temper it. Pour tempered milk into the soup.
Make a slurry with remaining 1 tablespoon of flour and 2 tablespoons of water. Stir slurry into soup and let simmer for 30 more minutes.
After soup has simmered add prawns and frozen corn. Cook 5 more minutes or until shrimp is pink and cooked through. Remove bay leaf. Stir in reserved bacon.