Hmmm OK, future me: add prompts everywhere like you wanted 😅
You go up the hill, through the patches of long grass. There should be a short wall and a lone tree at the top of the hill, just behind the wall is the lighter. When you approach it should say "Lighter Pickup". Press E, the lighter will drop in the hole. Once Tev picks up the lighter you should be able to interact with items in the hole.
Final things you need to do:
Light the boiler
Create the correct chocolate shape, press the Produce button... Hope that helps. Sorry for the lack of prompts, it was a struggle to fit it all in as it was 😔

Thanks :). The plan was to have them drop constantly and players would have to move them into the cave and climb out but signal connections were throwing me about a lot and I had to just rush an end game trigger last minute.