Cook the beans as per on pack instructions. Drain and set aside.
Heat oil in a large saucepan that has a lid. Add celery, onion, garlic, capsicum and tomato paste. Fry gently for 5-6 minutes.
Add Cajun seasoning, mustard powder and paprika. Cook for 1 minute stirring continuously.
Add stock, water, canned tomatoes and bay leaves. Cover with lid and bring to the boil. Add cooked pinto beans and rice, cover with lid and allow to simmer gently for 10 minutes until rice is almost tender. Stir frequently.
Add prawns and cook for 3 minutes until just cooked through.
Serve gumbo into bowls and garnish with chopped parsley.