NOTE: Recipe may be doubled. May use frozen cooked shrimp, thawed. Double sauce if you like your fettucine extra saucy.
Gather and prep all ingredients (peel shrimp, grate cheese etc...)
Add 1 1/2 to 2 quarts water and 1/2 teaspoon salt to large saucepan (for boiling pasta;) set over medium heat.
In a medium saucepan, add butter and oil; melt butter over medium/medium-low heat.
Add garlic powder, garlic salt, white pepper and cream; stirring constantly, bring to a simmer for 2 to 3 minutes.
Meanwhile, increase heat to high under pasta water to bring to a boil. Add fettuccine pasta; return to boil, stir pasta with a fork to prevent clumping; reduce heat to medium/medium-high; boil 11 to 12 minutes.
While pasta boils, add cheese to simmering cream mixture, reduce heat to low/medium-low; stirring constantly, simmer until sauce is smooth and thickened, about 7 minutes.
Add chopped shrimp to sauce, stir and reduce heat to low. Taste for seasoning and add salt and/or pepper as desired.
Drain pasta, reserving some of the cooking water (just in case you need to thin the sauce or loosen-up the pasta.)
Immediately pour drained pasta into serving bowl or individual plates; pour shrimp & cheese sauce over pasta. Mix sauce with pasta before adding garnishes, if desired.
Sprinkle with a little bit of crouton crumbs and a pinch of parsley for garnish, if desired. Serve immediately.