To be merciful to myself I have a headcanon that one the first shake Jack got from Mrs. Butters was just that, a lovely smoothie for the growing boy, the subsequent ones had that oomph in them. And two, I believe Mrs. Butters probably didn't list all the special ingredients because she wouldn't be bothered (and probably is used to 'her' boys getting where the recipe is going with the mention of that start) AND we never got to know just what kinda jawbone she put in there, I mean, normally that's not quite without consequence for spells, yes? Coulda been like, the pulverized jawbone of a Nepalese Yeti or something for all we know. It's not like the boys know even the half of what is in the bunkers supply closets, right? LOL.