In Indonesia they use Bannana Leaf stuffed with Fish and spices to make something called Pepes. Depending on whether you use 1 wrap or two wraps of bannana leaf and the flame, the result is more charred or steamed.
Fish Fillet cut into small pieces
Onion or Shallot
Lemon Grass or Kaffir Lime Leaf or Basil
For some reason Tomato really adds something to this.
Sometimes we also put in some pumpkin
You could look up some recipes for Pepes Ikan. The way my wife like to make is very traditional, adding turmeric, candlenut, Kaffir Lime leaves, Coconut Sugar, etc.
I attached a picture. This is really my favorite dish. This is what we had for Thanksgiving. The best fish for this is a White fish like a Snapper. On the East Coast we would make it a lot with Cod, Fluke, Flounder, ova here, this is very good with fillets of Mu. But any fish will be good. Another way we make this which is Very delicious is with Squid or Octopus.
You roll up in Bannana leaf and then pin the edges with little pieces of bamboo. However.. another way to make this is using Parchment paper or would guess, sausage casings. For Bananna Leaves we cook on the grill, I like the added flavor of char. Some people will steam. If we are using Parchment paper, we wrap em up and then place those onto a cooking tray and bake in the oven. Reallllllllly good.
Found a video for you which shows traditional Balinese way of making. https://www.youtube.com/watch?v=L-8t6T4-srI