Toss prawns with salt, pepper, Cajun seasoning and Oregano, heat a large pan over medium high heat and drizzle with olive oil. Add the prawns and cook for 2 minutes. Flip and cook another minute or two. Then remove to a plate and set aside. Drizzle pan with a little olive oil, add chorizo and brown until nicely caramelised, Remove to plate, set aside. Add pasta to salted boiling water and cook until al dente.
Lower heat to medium and add a bit more olive oil to the pan, add the onion, pepper, Cajun seasoning, brown sugar, and a generous pinch of salt. Sauté until softened a bit. Add the garlic and cook until fragrant, about 30 seconds.
Add crushed tomatoes, chicken broth and cream. Bring to a simmer, stirring and scraping up any brown bits from bottom of pan, simmer a 5 minutes, then add Parmesan and stir into sauce. When Parmesan is blended in, add cooked pasta, prawns and chorizo and stir to combine and heat through, season and finish with chopped parsley.