Cut fat (about a third of an inch) cross sections of fresh Maitake mushrooms. Coat the bottom of a flat-bottomed pan with olive oil. Over high heat, sear both sides of the Maitake slices until they just begin to release their liquid. Throw seared mushroom slices into a vat of Teriyaki sauce and let sit on low hear for about 45 minutes. Serve as a side with fish or poultry, or slice and serve over rice or pasta.