I've made tons of Mac & Cheese. My husband has eaten tons of same. The same tired problem. It's pretty okay when first eaten, but when reheated, it's dry and tasteless. Well, with a little help from my friends, and I thought or two of my own, I got it! Hubby declared it the "BEST" he'd ever eaten. If you like this recipe, see more at mybestcookbook.wordpress.com
Melt butter in large sauce pan, add the flour, make a roux. Cook for one minute. Stir in warmed milk.Heat and stir until it comes to a boil and thickens. Take off the heat.
Add the shredded cheeses and the cream cheese. Stir until all is melted. Add your macaroni. Stir until thoroughly encorporated.
If using the onions and bacon, add them now, and pour into a serving dish. Cover with the toasted bread crumbs and serve.
Note: the creaminess comes from the cream cheese. Do not omit this. Carla at THE CHEW came up with this idea, and the onions and bacon are her ideas as well. With them, this is pretty much a whole meal.