Macaroni and Cheese Pizza

I used to be a recipe cook, but recently I have gotten more creative (brave?).  I tried something today that turned out nicely so I thought I would share my "recipe."  I made this up after scrolling through half a dozen on-line recipes, but it's not really based on any of them.
The occasion:  it's my oldest daughter's 15th birthday and she has some friends over for games.  We were talking about what to have and of course pizza was suggested; it always is.  So was mac and cheese because my mac and cheese is awesome.  Hence, macaroni and cheese pizza!
I used a refrigerated pizza crust, which I normally wouldn't do but hey! it's been a week.  So, I spread the crust on a greased pizza pan and sprinkled it with some shredded mozzarella cheese.

Then I made an abbreviated version of my usual scratch mac and cheese recipe.  Cooked enough macaroni to make about 3 cups.    Melted half a stick of butter, then stirred in about a teaspoon of salt and ground mustard and about 2 Tablespoons of flour.  I didn't measure the seasonings or flour- at this point you are aiming for a wet paste consistency.  Then I added a Tablespoon of parmesan cheese and a cup of milk.  When that made a nice soup I added two cups of mozzarella- this is where is got different from just being awesome mac and cheese, for which I use cheddar.  Mozzarella goes on pizza!

Anyway I cooled that mixture some and spread it on the crust and baked it for 20 minutes at 400 degrees.  I considered putting bread crumbs on the top, but we don't have any, so I didn't.
 The kids said it was pretty good and they ate it all so I don't have a pic!  If you try this, let me know what you think!