Boil water in a large pot. Cook the penne pasta according to the package instructions.
After that, season the peeled and deveined prawns with Cajun seasoning (or any other seasoning of your choices like garlic powder or Italian seasoning).
In a large pan, heat some olive oil over medium heat. Once the oil is hot but not smoking, add the seasoned prawns. Cook the prawns for about 2 minutes on each side until they are cooked through and turn pink. Once cooked, remove the prawns from the pan and keep them warm.
While the pasta is cooking, prepare the Alfredo sauce. Melt a stick of butter in a large skillet.
After that, Pour a couple of cups of heavy whipping cream into the melted butter. Stir it in order to combine the cream and butter.
Grate fresh Parmesan cheese into the sauce, adding more as needed.
Whisk the sauce to mix all the ingredients well. Simmer the Alfredo sauce over medium-low heat until the cheese melts and the sauce thickens while whisking. Avoid boiling the sauce. Taste the sauce and add it with salt, pepper, and garlic powder if needed.
Once the penne pasta is done cooking, drain it before adding it to the hot Alfredo sauce in the skillet.
After that, Stir the noodles and sauce together under low heat, thoroughly warming them.
Serve the Shrimp and Sausage Alfredo Penne on individual plates. After that place a portion of the hot pasta with sauce on each plate and top it with pan-seared prawns. Sprinkle some shredded Parmesan cheese and dried parsley on top of the dish.
Serve the Shrimp and Sausage Alfredo Penne immediately while the pasta is still hot.