Hamburger Pie ("Favorite Casserole")

Last night I made an old classic casserole that Justin grew up eating.  His family called it favorite casserole, but it's really hamburger pie.  It's a lot like shepherd's pie...beef, potatoes and veggies.  We haven't had it in a long time, but Justin requested it.  And it kind of sounded good to me :P  As long as you have mashed potatoes it's very easy to make.  I made mashed potatoes in the morning so that prep was easy at dinner time.  I'll post the recipe as it's written (from my MIL) and add my mods.  As far as casseroles go this one is pretty good.  I wouldn't call it my "favorite" :P  But maybe that's because I didn't grow up eating it.

Hamburger Pie

1/2 lb. ground beef (I used a full pound...that's how my beef is packaged...and we like it meatier)
1/4 cup chopped onion
mashed potatoes (as much as you like, at least enough for a thin layer on top)
velveeta cheese (slices to cover the top.  You could easily substitute any good quality shredded cheese here.  We did use velveeta last night...I have some in the fridge...and it sounded good to me :P)
salt and peper to taste (I also added garlic powder)
1/2 can tomato soup (I used homemade.  And when I did use canned I always used a whole can)
1 can green beans (cut or french style) (I used cut beans from our garden...note to self, cook them first instead of just thawing them.  Else Justin will pick them all out :P)

Heat oven to 350.  Brown meat with onion.  Drain.  Season.  Stir in beans and soup.  Pour into ungreased 11x7 pan (you could use 9x13 if you want a thinner layer...just be sure to have enough potatoes to cover it).  Spread potatoes over top.  Top with cheese.  Bake until hot and top is slightly brown (30-40 min.).