Here's the recipe I generally used today:
http://www.mccormick.com/Recipes/Casseroles/Tex-Mex-Macaroni-Casserole.aspx .
I didn't use onion or corn, and they don't quite have tomato sauce here so I used passata (sieved tomatoes, so close enough). Also, they didn't have diced tomatoes so I got chipped with rich tomato juice (close enough). Finally, I added a little bit of hot sauce to the whole mixture, and a little salt & pepper to the ground beef while cooking it (I'd have also used garlic, but ran out). Oh! And I didn't know what 2 cups meant exactly so used the whole package of shells (I prefer them to elbows), which meant I needed to add a little more water to it).
Verdict: Turned out well. I did actually initially measure 2 cups of pasta, but it didn't look like much, especially considering shells are mostly space, so I added another cup, and then decided to just add the whole thing. It turned out OK, but for the sake of quantity, I'd prolly only use half the package when I make it again. Also, I topped it with chedder, but I secretly wanted to try Red Leicester on it... Might do tomorrow or something.