fancy mac and cheese (revised from pioneer woman)

2 cups (aprox) slice mushrooms
Watkins cooking spray
salt and pepper to taste
1 pkg bacon, cut into bite sized pieces
1 large onion, sliced thin
1/4 - 1/2 cup butter (I didn't measure)
1/2 cup fresh shredded Parmesan cheese
1 1/4 cup Mozza
1 1/4 cup cheddar
4 cups macaroni (maybe 5 cups but no more; I made 6 and had WAAAY too much)
1/4 cup flour
2 1/2 cups milk
2 eggs, beaten

Spread mushrooms in Costco pan lined with parchment paper. Spray well with cooking spray and bake @ 425F 25 minutes until deep golden brown. Set aside.
Fry bacon until only chewy, not crisp. Set aside on paper towel to soak up all that fat.
Saute onions till golden in bacon fat. Set aside. I drained these in a sieve. (I can't stand too much grease!)
Cook mac until almost done. Drain and set aside.
To make sauce melt 4 TBSP butter (aprox) in saucepan and whisk the flour into the melted butter. Slowly pour in the milk, stirring until thick. Add salt and pepper to taste. Spoon about 1/4 cup hot white sauce into a small bowl containing the beaten egg, stirring the egg with a fork as you drizzle it in. Then pour the mixture into the pot with the white sauce, stirring constantly. Add all that cheese.
Stir cheese sauce into the macaroni, adding milk to thin as necessary; I added quite a bit.
Layer into well-sprayed 9x13 pan like this: 1/2 the bacon,onion and mushroom, then 1/2 the mac. 1/2 onion and mushroom, 1/2 mac and then 1/2 bacon. If you wanna add more cheese on top, by all means do! I didn't and we loved it.
Bake @ 350F 1/2 an hour or so or until bubbly and hot. Enjoy!