Heat oil in a medium frypan over medium high heat and cook chicken until no longer pink and juices run clear.
Stir in sausage and cook until evenly browned. Drain chicken and sausage then set aside.
In a large heavy saucepan over medium heat blend olive oil and flour to create a roux. Stir constantly until browned and bubbly. Mix in garlic and cook about 1 minute.
Gradually stir chicken stock and beer into the roux mixture. Bring to a boil and mix in celery, tomatoes, onion, diced tomatoes, red chillies, parsley and Cajun seasoning. Reduce heat, cover and simmer about 40 minutes stirring often.
Mix chicken, sausage and prawns into the broth mixture. Cook stirring frequently for about 20 minutes.