Build the right block, activate it with the mob's item, and keep the fuel topped up. From there, the farm keeps producing on its own, even while you're offline, and the drops are waiting when you get back.
From the Overworld to the Nether, with drops matching vanilla's real loot tables.
Automatically stores XP from every farm in the chunk. No need to touch it.
For the most valuable mobs, capture their soul by really killing them first.
Tune drops, xp, fuel and durability without touching any code.