Heat grill to medium. In small bowl, whisk together hoisin sauce and 1 tablespoon oil; set aside.
Halve eggplants lengthwise; slice a bit off the skin side so they lie flat, and score both sides in a crisscross pattern.
Brush both sides of eggplant halves with remaining 1 tablespoon oil, and season with salt. Grill until charred and tender, 4 to 7 minutes per side. Brush both sides generously with reserved hoisin mixture; grill each side again just to glaze, about 1 minute per side. Serve hot.