Low-fat Alfredo sauce sounds like an oxymoron, especially when you consider its original incarnation: The traditional version consisted of copious amounts of butter — about 1/2 pound for four servings — and an equal amount of Parmigiano-Reggiano. Tastes have changed since the early 20th century, when the sauce gained its first taste of fame, and modern Alfredo typically contains heavy cream, butter and cheese; the cream helps disperse the cheese over the fettuccine and imparts a lustrous texture. Although there isn’t a true substitute for fat, you can recreate the same velvety mouthfeel of real Alfredo using a touch of starch and milk.

Liaison and Starch Thickened

This version of low-fat Alfredo relies on liaison — a French technique that combines one egg yolk with 2 ounces of cream to thicken 1 cup of sauce — as its primary thickening and creaming agent and utilizes the residual starch in the pasta water and a pinch of corn starch as secondary thickeners. This combination alleviates the need for all except 2 ounces of cream and 2 tablespoons of butter. It also contains a touch of olive oil for palatability.

Low-Fat Alfredo I

Whisk together 1 egg yolk and 2 ounces of cream until smooth and set aside. Add 5 to 6 ounces of grated Parmigiano-Reggiano to a mixing bowl for every pound of fettuccine you plan to make; 1 pound of pasta serves four to six people. To the cheese, add a generous pinch of cornstarch, a pinch of salt, a drizzle of olive oil and the liaison. Whisk the ingredients enthusiastically and set them aside.

Boil 1 pound of fettuccine in a 2-quart saucepan until al dente; the size of the pan and amount of pasta are integral to attaining the most starch concentration in the water. Drain the pasta and reserve about 2 cups of the water. Toss the pasta with a touch of butter or olive oil and set aside.

Pour 1 to 1 1/2 cups of the reserved pasta water to the bowl of sauce ingredients and whisk to incorporate it. Add the sauce to the saucepan and bring it to a simmer, stirring constantly. Season to taste with kosher salt and freshly ground black pepper. Add the fettuccine to the sauce and toss to coat.

Flour Thickened

Flour-thickened Alfredo contains 1 tablespoon of butter per cup of sauce, giving it the least fat content of the two low-fat options. This Alfredo is based on bechamel, the classic French “mother” sauce that consists of thickened milk; you can use any type of milk — whole, 2 percent or skim — but 2 percent provides the best balance of creaminess to lightness.

Low-Fat Alfredo II

For 2 cups of Alfredo, melt 2 tablespoon of butter over low heat and sprinkle 2 tablespoons of general-purpose flour over it. Cook the flour until it has a golden color, about 6 or 7 minutes, whisking occasionally. Next, pour in 2 cups of room-temperature milk; add a tablespoon or so at first; whisk to combine; then add the rest. Bring the sauce to a gentle simmer and continue whisking until it’s free of lumps.

Season the sauce with freshly ground black pepper to taste. Next, add the grated Parmigiano-Reggiano to taste, about 1 tablespoon at a time; let the cheese melt before adding more or it will develop a stringy consistency. Season the Alfredo to taste with kosher salt and, if needed, adjust the consistency with milk.

Dairy-Free Alfredo

You can make a simple, low-fat Alfredo with all the creaminess of the original and none of the lactose. Real Parmigiano-Reggiano cheese is lactose-free: During aging — true Parmigiano-Reggiano requires a minimum aging of 12 months — the lactose is converted to lactic acid, which doesn’t produce the negative effects that lactose has on the lactose-intolerant.

Low-Fat Lactose-Free Alfredo

For 2 to 3 cups of Alfredo, cook 3 tablespoons each of olive oil, flour and vegetable stock over low heat until thickened, about 3 minutes. Stir in 2 cups of soy milk or almond milk and bring to a simmer, whisking until free of lumps. Add grated Parmigiano-Reggiano to taste and season with kosher salt and freshly ground black pepper.