Chicken Alfredo

Method

1. grate4 min
   fine rasp, cheese cold
   parmesan on the smallest holes you own — pre-shredded cheese is coated in cellulose and potato starch that will not dissolve, and coarse shreds melt into threads instead of into sauce. Let the grated cheese sit out while the water heats; cold cheese hitting warm butter is the most common cause of a stringy pan.
2. sear10 min
   medium-high, dry surface, salted both sides
   Pat the chicken dry, salt both sides, and sear in the oil until an instant-read thermometer says 160°F at the thickest point — about 5 minutes a side. Rest it on a board while the pasta cooks; slice against the grain just before the toss, and fold the slices in with the pasta at the emulsify step. Resting first matters: sliced hot, the juices end up on the board instead of in the meat.
3. boil9 min
   rolling boil, salted, uncovered
   water + salt + fettuccine, stirring for the first minute so the strands do not weld. Use less water than usual for pasta — you want it cloudy and thick with starch, because that starch is the emulsifier that holds butterfat and cheese in suspension. Pull the pasta one minute short of the package time and reserve 1.5 cups of the water.
4. mix1 min
   wide pan, off the heat
   butter + 0.5 cup hot pasta water in the pan, swirling until the butter melts into a cloudy, slightly thickened liquid. Off the heat is deliberate: melted butter over a flame separates into oil and milk solids, and once it has split it will not carry the cheese.
5. emulsify2 min
   off the heat, tossing constantly
   drained fettuccine + buttery water, tossing hard so the noodles release their surface starch, then + parmesan in three handfuls, waiting for each to disappear before the next. Adding the cheese all at once drops the temperature unevenly and the casein clenches into a rope around the tongs; adding it above about 175°F does the same thing from the other direction. Splash in more pasta water whenever the pan looks tight — the finished sauce should slide, not cling.
6. season1 min
   warm, plated immediately
   + black pepper + nutmeg, then serve straight from the pan. Parmesan is already salty, so taste before adding any; and there is no holding this dish — the emulsion stiffens as it cools and reheating breaks it for good.