This is a flat mushroom that is warm to the touch. If you were to say to this mushroom "Warm it up, mushroom," the mushroom would likely reply "I'm about to." If you were to then say "Warm it up, mushroom," it would reply "That's what I was born to do."
You eat the warm flat mushroom. Much as you would expect, it warms you up inside. It doesn't flatten you up inside, though, because that sounds like it would hurt.
The description of this item refers to the song Warm It Up by the rap duo Kris Kross from their 1992 album Totally Krossed Out, which repeats the lyric "Warm it up Kris, I'm about to. Warm it up Kris, cause that's what I was born to do" in its refrain.