Well he boiled the butter - that helps make the cookies candy-like.
After that, ss near as I can see, he just wanted the cookies to go into the oven cold – so that they didn’t flatten out.
Nothing to add to the great posts above, just a couple FYIs.
Many curious cooking questions are addressed in this seminal book.
Tip for adding cold butter for flakey goods: Freeze it first, then use a cheese grater.
I’ve made the same recipe (Babish is awesome), and I found that the butter was rock hard after 60 minutes in the fridge.
I don’t make cookies very often. Oreos are good enough for me. Besides, too many cookies don’t bode well with my diabetes. Stupid pancreas!
But, biscuits? Now you’re talking my language.
I freeze a stick of butter, then use a box grater to shave it into the dry ingredients when I make my cat-head buttermilk biscuits. Sometimes I grate some frozen lard in the mix, too. Use White Lily flour (red winter wheat)—it makes a difference. Don’t use a rolling pin, but gently fold the dough a few times by hand before cutting. Result: high rising, super flaky biscuits.
The reasons for using frozen fat in dough have been touched upon up-thread, so I won’t explain further. Just do it. It involves chemistry and quantum mechanics and astrology and lots of other high-brow subjects you struggled with in school. Just freeze your fat and shave it into your flour; you don’t need to understand why it works. Think of it as magic.
Crack those cat-heads open (to the fluffy feline “brains”), pour lots of heavily peppered sausage gravy on top and boy-howdy, you’ve got yourself a lip-smacking Southern breakfast!
If you don’t have time to make the gravy from scratch a good canned version will suffice (although sausage gravy is simple enough to make). But, if you don’t have time to make your biscuits from scratch, don’t bother—eat a bowl of Captain Crunch instead.