Separate the tenderloins from the breasts. Between sheets of plastic wrap, pound the thicker side of the breast to make it more even in thickness. Season the chicken with salt. Heat the sesame oil in a large skillet over moderate heat. Add the chicken breasts and tenderloins. Saute for about 4 to 5 minutes. You'll know to turn the chicken over when the top looks opaque (tenderloins may take only 2 to 3 minutes per side.) Saute on the other side 4 to 5 minutes or until the interior is cooked through.
Remove the chicken to a plate. Deglaze the pan with the garlic and Chinese 5-spice powder and add the broth and hoisin mixture. Boil down covered until thick and glossy. Remove the skillet from the heat and whisk in the butter. Spoon the sauce over the chicken and sprinkle the scallions and cilantro on top.