½ pound (2 sticks) unsalted butter (preferably European style), at room temperature and sliced
½ pound finely grated parmesan cheese (preferably Parmigiano Reggiano)
Kosher salt, to taste
Bring a large pot of water to a boil, then salt generously with kosher salt. Cook the fettuccine, stirring often during the first 4 minutes and occasionally after that, according to package directions, until al dente.
Drain the pasta, reserving 1 cup of pasta water (or more to reheat the pasta later, if you predict you will have leftovers).
Return the pasta to the pot, off heat, and stir in the sliced butter, a small pinch of salt, half the cheese and a splash of the reserved pasta water (about ¼ cup). Toss the pasta vigorously, adding the rest of the cheese and more pasta water as needed for the sauce to emulsify. If you are having trouble getting the cheese to melt quickly, it's okay to turn the heat on low under the pot. Just work quickly so the sauce doesn't curdle.
Serve on warmed plates (see notes) with more parmesan cheese and a fresh grinding of black pepper.
Notes:
How to Warm Plates
Stack your plates or bowls and place them in the oven, at its lowest setting (usually 150ºF), for 15 minutes. Alternatively, if your plates/bowls are not oven safe, just run them under hot water and dry with a kitchen towel before plating the food.
Authentic Alfredo sauce tends to want to solidify when served in cold plates, due to the temperature shock.
Storage and Reheating
While fettuccine Alfredo tastes best when freshly made, that doesn’t mean you shouldn’t enjoy your leftovers!
The leftovers will keep in the fridge for up to 5 days, stored in an airtight container. They do not freeze well.
Reheat on the stove, over medium-low heat, adding more water (or pasta water, if you remembered to save extra) and butter.
