Prep Ingredients: Begin by preparing the vegetables. Cut the medium eggplants into bite-sized pieces, ensuring they are evenly sized for consistent cooking. Thinly slice the red and yellow bell peppers and the onion into thin strips. Mince the garlic and thinly slice the red chilies (if using). Measure out the Thai basil leaves and set aside.

Stir-Fry: Heat vegetable oil in a large pan or wok over medium-high heat until shimmering. Add the minced garlic and sliced red chilies (adjust quantity for desired heat) and stir-fry for about 30 seconds until fragrant, being careful not to burn them.

Add Vegetables: Add the prepared eggplant, bell peppers, and onion to the pan. Stir-fry continuously for 5-7 minutes or until the vegetables are tender-crisp and slightly caramelized. The eggplant should absorb some of the oil and become tender.

Sauce: While the vegetables are simmering, whisk together the soy sauce, oyster sauce, fish sauce, and sugar in a small bowl until the sugar completely dissolves.

Combine and Finish: Pour the sauce over the stir-fried vegetables in the pan. Stir well to coat all the vegetables evenly with the sauce. Let it cook for 2-3 minutes, allowing the sauce to thicken slightly.

Add Thai Basil and Season: Add the Thai basil leaves to the pan and toss everything together until the basil leaves wilt and release their aromatic flavors. Season with salt and pepper to taste, adjusting as needed.

Serve: Transfer the Thai Eggplant Stir-Fry to a serving dish. Serve hot with steamed jasmine rice, allowing the flavors to meld together for a delicious and satisfying meal.