In vanilla Minecraft, huge fungus have a 6% chance to naturally generate with a thick stem.
This ability is not available when you bone meal a fungus.
This mod lets you grow huge fungi with a thick stem by placing 5 fungi in a plus shape.
Works for both crimson and warped fungi.
Designed for 1.20.0-6, but might work with older versions.
Please create an issue if you find a compatible version which is not listed.