This is a link to the last time I talked about this here:

https://news.ycombinator.com/item?id=16534745

and to the particular comment in that subthread where I give the recipe itself:

https://news.ycombinator.com/item?id=16540539

EDIT: actually, let me also just paste the recipe here:

    3¾c. of brownie mix (again, Betty Crocker Original Supreme)
    2 eggs
    ¼c. water
    ⅓c. vegetable oil
    and the included packet of Hershey's syrup

As of the original redesign mentioned in [the 2018 article I'm pasting this from], the amount of brownie mix in a box was cut back to 3 cups, the recipe involved 1 egg instead of 2, and I don't remember how the water and oil were affected but they were different.

Ok so this is the cake pan thread.

They can shrink the amount of mix in a box but the hard limit of shrinking is the standard set of pans that everyone has. There are also bundt and springform pans in addition to the rectangulars. So if they shrink the amount in the box, as the original article mentions, they have to keep changing the recipe to increase the air and the rise so it still fits the same pans -- maybe badly. Or they just abandon the larger pans and don't offer instructions for them and it's up to the baker to buy multiple boxes and do the math?