Cook the fettuccine pasta to al dente according to package instructions.
Clean the shrimp and pat dry with a paper towel.
Season the shrimp on both sides with salt and pepper.
In a deep skillet, melt 2 Tbsp of butter. Add the shrimp into the hot skillet and cook for 2 minutes per side.
Once cooked, remove the shrimp from the skillet and set aside.
To the same skillet, add 4 Tbsp of butter and minced garlic. Cook until the garlic is fragrant.
Add the heavy cream, milk, flour, and parmesan cheese to the pan. Whisk lightly until combined.
Keep the heat low-medium, and bring the sauce to a light simmer. Allow the sauce to thicken up slowly without allowing it to boil.
Season the alfredo sauce with a pinch of salt and pepper to taste.
Once the sauce has thickened, add the cooked noodles to the sauce and mix lightly without breaking up the noodles.
Add the shrimp back into the skillet and mix lightly.
Garnish the pasta with fresh parsley and extra-grated parmesan, and serve!