"The Maine Diner's" Macaroni & Cheese (my version)

Life As Mom is hosting a Comfort Food Recipe Swap today...as I'm feeling a little under the weather I could use some comforting right about now!!

For my contribution, here is my favorite macaroni and cheese recipe. It's to replicate the mac & cheese from the "Maine Diner"... up in Maine on Route One, of course, where my parents are part-time. I don't actually know their recipe, but it's one of their specialties and this tastes just like it! If you're ever up that way, it's a must to check out!!
I don't have a picture to add yet, but come back next week and I will be serving this at my "New England Saturday Night" dinner for Family Fun night and I'll have pics!

1box elbow macaroni
2C. shredded white american cheese (keep some aside for the top before baking)
1/2C. shredded cheddar cheese
2T. flour
2T. powdered milk
1 1/4C. boiling water
1/4t. salt (I omit)

Cook macaroni accoriding to pkg. directions. Drain. Mix powdered milk and flour together. Add boiling water. Add cheese and stir until thick and smooth (I usually do this in a glass mixing bowl, then pop in microwave for 20sec. intervals, stirring, until no lumps) Grease casserole dish and pour in pasta, then pour cheese mixture over and mix together. Spread some american cheese on top. Bake in 350deg. oven until bubbly and cheese is melted. (about 20-25mins)
**If you like a crunchy top, mix 1C. bread crumbs with 2T. butter and sprinkle on top of casserole before baking. Bake until crunchy.