Easy, and just the way Mom made it!
The key is GOOD CHEDDAR! Depending on where you live, use the best you can get. I like Wisconsin (and I have a source), but NY, Vermont, or Tillamook from Oregon will do.
1. I use TWO POUNDS of cheddar per pan. Yes, I said 2 pounds. If you are worried, don't make this. If you make it, use the cheese. Cut cheese into 1" x1" slices. I counted. I had about 180 slices...not too thick.
2. Make a white sauce (bechamel). I use 3T. of butter, 3T of flour, 1/4 t. salt for each cup of milk. For this batch of 1.5 lbs of penne, I used 4 c. of milk. Melt butter, flour and salt. I also add pepper. Add milk and stir until it boils and thickens. Remove from heat.
*Do NOT use skim milk (I used 2%), but skim milk is what we drink and use in coffee or on cereal. I made myself remember to buy a quart of what we call "real milk"
(While it is cooking, boil your pasta.)
3. Pour half of drained penne into baking dish (9x13). Toss with half of bechamel. Top with 1/3 of cheese. Stir remaining drained pasta into pan of sauce to coat well. Spread in pan. CRAM in the rest of the cheese. Use it all.
It looks like this unbaked:
Bake at 350 for 35-40 min.