Ready for a deep dive? This recipe from Tested Tried and True (Junior League of Flint, Michigan, Incorporated, second printing, April 1976) is just begging to be unpacked.
If you're asking when you might need a Chicken Broccoli Casserole for 500, that question is answered by the end note, as this was "Served at the Flint Institute of Music Gourmet Sale and prepared by 20 dedicated souls." So, apparently, you're supposed to sell this casserole in support of music? And it's easy enough for souls to prepare? (I prefer human cooks, myself.)
First of all, I love that this starts with the assumption that we've already stewed and boned 50 chickens before we even started. We are apparently very ambitious.
Next, I love the measurements. Most of them try to be user-friendly, noting, for example, that you'd need 50 sticks to get the necessary 12-1/2 pounds of butter. The flour, though-- rather than giving the number of cups and/or pounds of flour, the recipe asks cooks to measure out 300 tablespoons! I can just imagine someone standing there, counting tablespoons of flour out loud. "Okay, 127, 128, 129..." Then some wiseass walks by yelling "72, 96, 153!" Then the wiseass is covered with about 132 tablespoons of flour and somebody new has to start over counting out 300 tablespoons.
Third, I love that the recipe never tells how many 9 x 13 x 2 pans this will take, anyway. At least simple math tells me that it will be anywhere from 42-50 if each pan serves 10-12 people, but it would have been nice to know that up front rather than having to figure it out myself.
I love that the end of the recipe instructs cooks to "Serve with pear halves and muffins for a late supper," as if this is something we've just casually thrown together for a weeknight dinner when everyone was running late.
And finally, I love that the recipe is soooo enormous! I mean, unless you have access to an industrial kitchen, who is even going to be able to cook on this scale? Cramming 20 people into even a really nice home kitchen is just not going to work, and those blessed with a double oven would still be hard-pressed to cook at least 42 trays of Chicken Broccoli Casserole in any reasonable amount of time. Why not, you know, scale it down to serve 25 or 50 and ask multiple people to bring over a batch? That seems way more practical.
Whoever owned this book before me seemed to have had a similar thought-- as it looks as if they were trying to scale it down to 1/50th of the original! I so wish I knew if they managed it! And how it turned out if they did! And why they insisted on using this recipe rather than the one of the other much more reasonably sized chicken broccoli casseroles in the same cookbook. The world will never know, but I salute you, unknown cookbook owner who was just as intrigued by this recipe as I was.