I’m not 100%, but I think it’s 降られる.
“I was writing down how to make it in the recipe book, when suddenly (what Aiko-san just said) fell upon me.”
Essentially, she had a slightly delayed reaction to suddenly being told she was going to be the one to make it. That was the only sense I could make of it, anyhow. Perhaps someone else disagrees.
Per weblio:
“Generally an abbreviation of a phrase used to request a favor such as 「そこをなんとかお願いします」. It is used in a situation where you insist on doing something the other party is reluctant to do.”
Since that is a grammar point, then I would say that works fine. I honestly just automatically filled in like a したことない afterwards in my head, since I didn’t know that grammar point (I really should buy that book…). There’s definitely something implied after it that indicates she hasn’t done this kind of thing since that time period, regardless of what it is.
I also don’t have any sources besides some random ones on the internet I’m not positive I trust, but it makes sense to me that it’s something like this.
For my own analysis, if I were to not trust the sources:
I think it’s a case of Japanese being vague again, and assuming you know what will follow; she was just raving about the flavor of the other food, so it’s a fair assumption that she is about to do the same here.
“Moreover, if I were to talk about the deliciousness of the potato salad, (then I would have to say it’s also great… or something else positive here; sorry, not very imaginative at the moment apparently. 
).”
Edit: Actually, Maggie-sensei has a section that mentions といったら! It’s listed with the というと section, and she mentions that it’s used for expressing your opinion on something, and can be either positive or negative. The example she gives that’s most similar:
Though obviously, context tells us in our case, that it’s positive.
