Cook pasta according to package directions. Drain and set aside.
Meanwhile, in a large bowl, toss the shrimp with half of the Cajun seasoning and 2 tablespoons of the olive oil.
Place remaining olive oil into a large deep sided skillet and warm over medium-high heat until shimmering.
Add shrimp and cook for 4-5 on each side. Remove shrimp to a paper towel lined pan and set aside.
Add the heavy cream to the remaining oil and seasonings in the pan. Whisk in garlic salt (to taste), remaining Cajun seasoning, and black pepper (to taste).
Sprinkle in the grated parmesan cheese and heat through until cheese has melted. Bring sauce to a gentle boil.
To thicken the sauce, make a slurry from the cornstarch and water. Whisk the slurry into the sauce in the skillet. Cook an additional 2-4 minutes to thicken.
Add cooked pasta and shrimp to the skillet and stir to coat.
There is salt already added in both pre-bottled and our homemade Cajun seasoning, so feel free to omit the extra garlic salt called for above if desired.
You can use frozen or fresh shrimp, but if they are frozen, allow them to thaw completely before beginning and pat them dry. You can typically find grilling shrimp at the seafood counter at your local grocery store.
Penne pasta is our go-to for this dish, but you can easily substitute it with your favorite noodle shape. Ziti, rigatoni, fusilli, and cavatappi are all great substitutes but even long noodles such as fettuccine, spaghetti, or angel hair would work well.
Shrimp does not take long to cook, which also means it can easily be overcooked. The shrimp will curl and turn opaque with pink and red hues when it is finished cooking. Overcooked shrimp tend to turn a whiteish grey and are rubbery in texture.
Store leftovers in an airtight container kept in the refrigerator for up to 3 days. Reheat on the stovetop over medium-low heat just until warmed through. You can add a dash of water or additional cream to loosen it back up if needed.