Where is the fillet steak from?
The fillet is the most tender part of the animal because it is an unused muscle that's purpose is just to give padding for the internals of the animal. Because it is unused as a muscle it has less lactic acid running through it thus making it tender but almost tasteless.
Chefs like using this because it is almost always tender and always comes with a sauce or dressing of some sort. That is why strong flavours are All weights are approximateAll weights are approximate