Creamy Parmesan Sauce

In a previous post I mentioned my famous 'white sauce.' Like most of my cooking, my white sauce varies depending on the ingredients I have available in the fridge or in the pantry. My white sauce has also changed through the years. What began as basically a cheesy white gravy has evolved into a rich and delicious creamy Parmesan sauce.
I wouldn't necessarily call this sauce an Alfredo sauce because I don't make it in the same manner, nor do I use the same ingredients as Alfredo, but it is very similar.
The ingredients and measurements haven't changed too much lately except for the use of evaporated milk. It was an accidental discovery one evening upon realizing I didn't have enough milk on hand. What I discovered was that the evaporated milk made the sauce creamy like half and half or whipping cream and gave a richness to the flavor.
The only other substitution I have made o late is the garlic salt. Sometimes I will use fresh pressed garlic instead of the garlic salt and use very little salt (1 tsp) to the sauce instead. I like it both ways. The fresh garlic does make the sauce MUCH more garlicky ;)

Ingredients:
1/2 cup or 1 stick butter
1 Tbs garlic salt with herbs (or less to taste)
1 tsp black pepper
1/4 cup flour
1 cup milk
1/2 cup shredded Parmesan cheese (fresh)
1/4 cup grated Parmesan cheese (canned)
1 can evaporated milk

Directions:
Melt butter in a medium sauce pan.
Add flour, garlic salt, and pepper.
Stir with whisk to combine and make a roux.
Add milk all at once.
Stir constantly until sauce begins to thicken.
Add shredded Parmesan cheese.
Stir with a spoon until cheese melts (Cheese will stick to the whisk).
Add grated Parmesan cheese and stir.
Add evaporated milk in small increments as sauce begins to thicken. Whisk to blend after each addition.
Taste sauce and adjust seasoning if necessary.