This is one of my family's favorites. It's one of my favorites because it's so easy to make. I got the recipe off a box, but I have tweaked it.
One box of Au Gratin Potatoes (I buy Kroger brand)
1 lb ground beef
1 can french style green beans, drained
1 can cream of mushroom soup
shredded casserole cheese
Brown your ground beef, drain
Prepare your au gratin potatoes according to the oven directions on the box. Mix in soup, green beans, and ground beef.
Sprinkle cheese on top for the last 5 minutes of cooking time. I add about a cup of cheese - that's where the "cheesy" comes in. :)
I'm sure this is supposed to serve 6 or 8, but we rarely have leftovers.