In a large pot or deep skillet, combine the fettuccine pasta, whole milk, chicken broth, minced garlic, salt, black pepper, and crushed red pepper flakes.
Place the pot over medium-high heat and bring the mixture to a gentle boil, stirring frequently to prevent the pasta from sticking.
Reduce the heat to medium and continue to cook, stirring often, until the pasta is tender and most of the liquid has been absorbed, about 12-15 minutes.
Add the unsalted butter to the pot and stir until melted and incorporated.
Stir in the freshly grated Parmesan cheese and heavy cream until the sauce is creamy and smooth.
Cook for an additional 2-3 minutes, stirring constantly, to allow the sauce to thicken slightly.
Remove the pot from heat and sprinkle the chopped fresh parsley over the pasta.
Serve immediately, garnished with extra Parmesan cheese if desired.