Im NOT the creator of this mod
Context: there are some typos in the .jar file. the original creator(@coringplay) was aware of this and even answered comments about it, but never decided to fix and repost it themself for some reason, and if they did, I couldn't find it so..
All I did was fix the typos they made("lava_generato" -> "lava_generator"). so now you can craft the "lava core" item after crafting the "lava core off" item(the typos restrict the recipe from showing up in JEI, so there was no way to know how to craft)
If you don't want to download this file, I put instructions on how to fix the issue in the comment section on the original page. here-> https://www.curseforge.com/minecraft/mc-mods/lava-generator/comments
Original Descrip.:
This mod adds a block that allows you to create an endless source of lava. But to create this block, you only need to find one object, which is the core of this block.
You can see the craft through jei.