Fish Glue!
You can substitute american gelatin with perfect results. I'm sure if you look on internet you'll find equivalents. It's the same thing, ground up, so no problem. Much easier to use, too.
I have a funny story about "colla di pesce" which i can't resist telling.
I wanted to make this fancy tart which is amazing, a brisee crust, a bavarian cream filling and strawberries on top spooned with melted redcurrant jam.
I had just come to italy, 30 years ago. I go to the local store and ask for GELATINA, thinking that means gelatin. It does, but it means the kind of savory soup gelatin that you would use for a meat dish, like to encase some cold meat salad or something. When i brought it home i realized it was no good. So i looked it up in the dictionary, gelatin is "colla di pesce" - which means, literally, fish glue.
I go back and ask for colla di pesce and the guy behind the counter says, oh, no, we don;t have that, you have to go to the hardware store.
Now to realize the situation at the time, salt and tobacco were both state monopolies, and they were both sold only in "tobacco stores" - actually called "sale e tabacchi" - salt and tobacco stores. You couldn;t buy salt even in a supermarket, even if you could FIND a supermarket in the 70s in rome! So i was already used to bizarre places to find familiar things, get salt in the tobacco store was no more bizarre than to get gelatin at the hardware store.
Fortunately the hardware guy knew more about cooking than the food store guy, and told me that was a cooking thing but i would definitely not find it in the neighborhood. Only very special downtown stores would have it. (People, contrary to popular belief, don't do home baking here, at least nothing more than some dry cake or a pudding).
But anyway, from then on i brought a box of gelatin from the states when i would go, and i use it for panna cotta, and it's fine. Just find the dosage equivalents. One sheet is much less than an envelope. But it;s the same thing. (Boiled bones and gristle).
