The original fettuccine Alfredo was made with a surprising ingredient: cooking water. When boiling pasta, enough starch leaches into the hot water to melt with the butter and make a creamy sauce. Use about 3/4 cups of cooking water per 1 pound of pasta and bring it to a boil with two sticks of butter. Add your cooked and drained pasta, sprinkle finely shredded Parmesan cheese in with the noodles and toss it over medium-low heat until the sauce is creamy and the pasta is coated.

If you are substituting for the cream in an Alfredo sauce recipe, you have several options. Cream varies according to the amount of butterfat it contains, and substitutions made with a lower fat dairy liquid such as regular or fat-free half-and-half or milk. If you're using these, substitute in equal quantities. Using whole milk will result in a richer sauce, but 2 percent or skim milk work just as well. You can also use canned evaporated milk, or reconstituted powdered milk. To maintain the richness of cream, substitute 3/4 cup of milk and 1/3 cup of butter for each 1 cup of cream called for in your recipe.

Combining dairy products can produce a rich-tasting sauce that's similar to Alfredo but lower in fat. Try cottage cheese and plain yogurt with seasonings such as garlic, lemon zest and black pepper, combined in a blender until smooth. Greek yogurt gives a thicker sauce. Stop yogurt curdling when heated by blending it first with 1 tablespoon of flour, or stirring it into the sauce after removing it from the heat. Sour cream blended with hot broth takes just a few minutes to whip up as an Alfredo alternative, but take care when spinning hot liquids in your blender, because they can splatter. To thicken your sauce, add 1 tablespoon of cornstarch and simmer over low heat without boiling, just until thick.

You can use nondairy products, substituting equal quantities. To adapt a recipe to make a diary-free version of Alfredo, substitute olive oil or soy margarine for the butter, and use unsweetened soy or almond milk. Begin by making a roux using a few tablespoons of flour mixed with the melted fat, fortified with either dry white wine or vegetable stock. Add the amount of cream called for in the recipe using soy or almond milk, and simmer until thickened. You can also blend soft tofu with nondairy sour cream to make a thick white sauce similar to Alfredo. Boiled cauliflower pureed in a blender and combined with broth and minced garlic makes for a white sauce made from vegetables.