GregMeth is a simple set of CraftTweaker scripts for GregTech: Community Edition that adds a complex chemical synthesis pathway for crystal meth, using machines and starting materials available in GT:CEu.
Download the latest release and extract the contents into your .minecraft installation folder. GregMeth requires CraftTweaker and GregTech CE: Unofficial. In game, you will need to enable the included resource pack in order for the names of items to appear properly.
Use JEI.