Fill your largest pot with water and season it well with salt — it should taste like mild seawater. Bring to a rolling boil over high heat.
Drop the fettuccine into the boiling water and stir immediately to prevent sticking. Cook according to package directions until just al dente — it should still have a slight bite since it'll finish cooking in the sauce.
⏱ 10 min
While the pasta cooks, melt the butter in your largest skillet over medium-low heat. Watch for it to foam and subside — you want melted butter, not browned butter.
Pour in the cream and let it simmer very gently — just tiny bubbles around the edges. This gentle heat prevents the cream from breaking and creates a smooth base for the cheese.
⏱ 2 min
Before draining the pasta, ladle out a full cup of the starchy cooking water and set it aside. This liquid gold will help bind your sauce. Drain the pasta quickly but don't rinse.
Immediately transfer the hot, dripping pasta to the skillet with the cream mixture. Use tongs to toss everything together, coating each strand with the warm cream.
Pull the skillet off the heat completely. Now add the Parmigiano-Reggiano in three additions, tossing vigorously with tongs after each addition. The residual heat will melt the cheese into a silky sauce.
If the sauce seems tight or clumpy, splash in pasta water a few tablespoons at a time, tossing constantly. You want a glossy sauce that moves like silk and coats the pasta completely.
Taste and adjust with salt and pepper — remember that Parmesan is already salty. A light grating of nutmeg adds traditional warmth if you're using it.
Plate immediately in warmed bowls and pass extra grated Parmigiano-Reggiano at the table. Alfredo waits for no one — serve it hot and eat it fast.