Step 1

Trim 1 pound eggplant and cut into 1-inch cubes. Place in a large bowl and cover with cold water. Let soak while you prepare the remaining ingredients.

Step 2

Prepare the following, adding each to the same medium bowl as you complete it: Cut 1/2 medium yellow onion lengthwise into 1/2-inch wide wedges. Trim, halve, and remove the seeds and membrane from 1 medium jalapeño pepper; cut lengthwise into 1/4-inch-wide strips. Thinly slice 2 garlic cloves. Peel and finely grate or mince 1-inch ginger until you have about 1 tablespoon.

Step 3

Trim and thinly slice 1 small Fresno chile crosswise if using. Place 1/4 cup water, 2 tablespoons oyster sauce, 1 tablespoon light soy sauce (or 1 1/2 teaspoons regular soy sauce and 1 1/2 teaspoons water), and 1/4 teaspoon granulated sugar in a small bowl and stir to combine.

Step 4

Drain the eggplant and pat dry with paper towel. Sprinkle with 1 tablespoon cornstarch and toss to coat.

Step 5

Heat 2 tablespoons of the neutral oil in a wok or large nonstick skillet over high heat until shimmering. Add the eggplant, spread into an even layer, and sear until browned in spots and starting to soften, 3 to 4 minutes. Add the remaining 1 tablespoon neutral oil and onion mixture. Stir-fry until the eggplant is tender and the mixture is fragrant, about 1 minute more. Add the sauce mixture and stir-fry until the vegetables are coated in sauce, about 30 seconds.

Step 6

Transfer to a serving dish and top with the Fresno chile if using.