Follow these steps carefully, as the technique is just as important as the ingredients. The process is broken down into three key stages: preparing the eggplant, mixing the sauce, and the final stir-fry.

Stage 1: Preparing the Eggplant (The No-Soggy Method)

1. Wash and Cut: Rinse the eggplants under cold water and pat them completely dry with a paper towel. Trim off the top stems. Cut the eggplants on a bias (a 45-degree angle) into pieces about 2 inches long and 1 inch thick. Then, cut these larger pieces in half or into quarters lengthwise, so you have long, wedge-like shapes. Consistent sizing is key for even cooking.
2. Salt and Rest: Place the cut eggplant pieces into a large colander set over a bowl or in the sink. Sprinkle them generously with the 1 tablespoon of kosher salt, tossing them with your hands to ensure every piece is lightly coated. Let the eggplant sit for 30-60 minutes.
3. Observe the Magic: During this time, you will see beads of moisture forming on the surface of the eggplant, and a brownish liquid will collect in the bowl below. This is the salt drawing out the excess water, which is the primary cause of soggy, oily stir-fries. This step also helps to season the eggplant from within and collapses some of its spongy air pockets.
4. Rinse and Dry THOROUGHLY: After resting, rinse the eggplant pieces thoroughly under cold running water to remove all the salt. Now for the most critical step: drying. Transfer the rinsed eggplant to a clean kitchen towel or several layers of paper towels. Pat them down, press gently, and do whatever it takes to get them as dry as humanly possible. Any remaining surface moisture will cause the oil to splatter violently and will steam the eggplant instead of searing it.

Stage 2: Mixing the Aromatic Stir-Fry Sauce

1. Combine Ingredients: While the eggplant is resting, prepare your sauce. In a small bowl, combine the soy sauce (or tamari), Shaoxing wine, Chinkiang vinegar, sugar, and the optional Doubanjiang.
2. Create the Slurry: In a separate tiny bowl, whisk together the cornstarch and the 1/4 cup of water or chicken broth until the cornstarch is completely dissolved and there are no lumps. This is called a slurry.
3. Combine and Set Aside: Pour the cornstarch slurry into the bowl with the other sauce ingredients. Whisk everything together until fully combined. Give it another quick stir right before you add it to the wok later, as the cornstarch can settle at the bottom. Having your sauce ready to go is a fundamental rule of stir-frying.

Stage 3: The Stir-Fry Assembly

1. Prepare Your Station: The stir-frying process is fast. Have all your ingredients prepped and within arm’s reach of your stove: the dried eggplant, the prepared sauce, the minced garlic and ginger, the separated scallions, and the optional ground beef. This is your mise en place.
2. Sear the Eggplant: Place a large wok or a heavy-bottomed skillet over high heat. Let it get screaming hot. You should see a slight shimmer of heat rising from the surface. Add 2-3 tablespoons of your high-smoke-point oil. Once the oil is shimmering, carefully add the dried eggplant pieces in a single layer. You may need to do this in two batches to avoid overcrowding the pan, which would steam the eggplant.
3. Develop Color: Let the eggplant cook undisturbed for 2-3 minutes per side, until it’s beautifully golden brown and slightly charred in spots. The eggplant will absorb the oil quickly; this is normal. The initial salting helps reduce how much it drinks up. Once browned, use a slotted spoon to remove the eggplant from the wok and set it aside on a plate.
4. Cook the Aromatics (and Beef): Reduce the heat to medium-high. Add the remaining 1-2 tablespoons of oil to the wok. If using the ground beef, add it now. Break it up with your spatula and cook until it’s browned and cooked through, about 3-4 minutes. If not using beef, proceed directly to the next step. Add the minced garlic, ginger, and the white parts of the scallions to the wok. Stir-fry for about 30-45 seconds until they become incredibly fragrant. Be careful not to burn the garlic.
5. Combine and Sauce: Return the seared eggplant to the wok with the aromatics (and beef, if using). Give the prepared sauce a final quick stir and pour it all over the eggplant.
6. Thicken and Finish: Gently toss everything together to coat the eggplant evenly. The sauce will bubble and begin to thicken almost immediately due to the cornstarch. Let it cook for 1-2 minutes, stirring gently, until the sauce is glossy and has thickened to your desired consistency, clinging to every piece of eggplant.
7. Final Touches: Turn off the heat. Drizzle the toasted sesame oil over the dish and toss in the reserved green parts of the scallions. Give it one final, gentle toss to combine. Serve immediately.