Heat the oil in a stir-fry pan or large skillet. Add the onion and sauté over medium-low heat until translucent. Add the garlic and continue to sauté until both are golden.
Cut the eggplant into ½-inch-thick slices, then slice the rounds into thick strips or dice.
Add the sherry, eggplant, and ginger to the pan, along with about ¼ cup water. Cover and cook over medium heat for 5 minutes, or until the eggplant is just tender. Lift the lid once or twice during that time to stir.
Stir the celery and hoisin sauce into the pan. Cook just until everything is heated through. Season to taste with soy sauce and hot sauce.
Stir in the scallions and cilantro, or use them as garnish. If you'd like, serve the dish over or alongside hot cooked rice or noodles. Pass around extra hot sauce and/or soy sauce for individual servings.