Most Italians will use what ever is on hand. and not always what some recipe says The main thing is the same type of ingredients can be used. We will be substituting a bit here also. Lastly, It is an "American" custom to use heavy cream to make alfredo, Not really that big a deal. Besides heavy cream is just too darn expensive and I do not have a cow in the backyard.
Also see: http://www.instructables.com/id/Our-food-instructables/
Step 1: What's needed:
Cooked Fettucine pasta.
1 cup shredded mozzarella cheese. Normally Parmesan cheese is used, but we are substituting here,
1 stick butter.
You can use a little milk, pasta water, or condensed milk if the sauce seems to thick.
Lots of pepper to taste.
Celantro, parsley, or etc to taste.
1/2 cup Parmesan cheese for topping finished product.
Note: some variation of this dish use egg yolk as part of the mixture.