Alfredo sauce has a storied history. It's widely held that traditional Alfredo, like most classic preparations, was borne from necessity: Roman chef Alfredo di Lelio created his namesake sauce as a duty to his wife, who, after childbirth, lost her appetite. Alfredo combined the finest butter and Parmigiano-Reggiano with wide, sturdy fettuccine noodles, and the pasta-eating world entered a new epoch. Attaining a creamy, smooth Alfredo requires managing its heat on the stove and using a fluid tossing-and-twirling technique to combine its components with the noodles.
Classic of Classics
When Alfredo sauce contains nothing more than butter, cheese and -- perhaps most importantly -- technique, you need the best of each to make the preparation stand out. You can master the Alfredo technique with repetition. The ingredients, on the other hand -- real Parmigiano-Reggiano and whole, unsalted butter -- have no substitute. This version of Alfredo gets its creaminess from a lifting-and-tossing motion of the noodles while judiciously incorporating a bit of starchy pasta water to thicken the sauce as needed.
Classic Alfredo consists of equal parts butter and Parmigiano-Reggiano; about 1/2 pound of each makes enough sauce for 1 pound of pasta, or about 5 to 6 servings. You need a relatively small pot for the amount of pasta -- a 6-quart part for 1 pound of fettuccine, so the starch is concentrated enough to thicken the sauce.
Classic Alfredo Technique
Tear the butter into pieces of approximately the same size and space them out in the serving dish. Tearing the butter by hand softens it. Grate an equal amount of Parmigiano-Reggiano and set it aside. Boil the fettuccine in salted water until it reaches the al dente stage, or, for about 7 to 8 minutes, and drain it, reserving approximately 3/4 cup of the water. Spread the hot pasta on the platter over the butter to melt it.
Sprinkle the grated cheese over the pasta in an even layer and slowly drizzle about 1/4 cup of the reserved pasta water over it. Using an oversized spoon and fork, lift the pasta from the middle of the dish; swirl the noodles; and return them to the dish. Next, collect more pasta from the edges of the dish; swirl, and return them to the center. Add a few tablespoons of pasta water -- the sauce will coalesce and smooth as you do -- and grind a few cracks of black pepper in the dish to taste. Continue lifting, twirling and mixing the pasta until the cheese, butter and pasta water form a smooth sauce and coat each noodle. Serve immediately.
Cream-Based Alfredo Sauce
Cream does more than add velvety smoothness to Alfredo sauce; it helps the cheese to disperse and coat the noodles without as much tossing and twirling as required in the classic technique. The inclusion of cream bears a few considerations, namely separation, scorching and graininess. Graininess, also referred to as "stringiness," occurs when cheese reaches between 170 and 180 degrees Fahrenheit. When cheese approaches boiling temperatures, its protein coagulates and separates from the fat and water. Once Alfredo separates, it won't return to its former structure; the addition of a little more cream might give the illusion of smoothness, but you can still detect a graininess on the palate.
The solution: Use an instant-read thermometer and keep the cream at around 160 to 165 F. You can also tell by how the cream reacts: When cream reaches 160 F, it produces small bubbles around the edge of the pan.
Cream-Based Alfredo Technique
Set out 1 part unsalted butter at room temperature and grate 1 part Parmigiano-Reggiano and set it aside; about 2 ounces yields about four servings of sauce. Bring 4 parts cream -- or 1 cup -- to a low simmer over medium heat, or to 170 F. Season the cream with salt and pepper and lower the heat to medium-low. Whisk in the butter, about 1/2 tablespoon at a time, until fully incorporated -- don't add more butter until the former emulsifies with the cream -- this prevents it from separating into a greasy pool on the surface.
Take the cream off the heat and boil the fettuccine to al dente; 12 ounces of pasta per cup of cream should suffice. Drain the pasta and add it to the cream. Toss the pasta in the cream while sprinkling cheese intermittently, cracking fresh ground pepper as you do so, to taste. Serve when the sauce is fully incorporated.