In a bowl, combine soy sauce, hoisin sauce, rice vinegar, brown sugar, chili garlic sauce, sesame oil, black pepper, and cornstarch. Mix until well combined.
In a wok or large skillet, heat vegetable oil over high heat. Add the eggplant and stir-fry for 5-6 minutes until tender and slightly golden brown.
Add garlic and stir-fry for another 30 seconds until fragrant.
Add the bell peppers and stir-fry for another 2-3 minutes until tender.
Pour in the vegetable broth and the soy sauce mixture. Stir-fry for another 2-3 minutes until the sauce thickens.
Add the green onions and roasted peanuts. Stir-fry for another minute until everything is well combined.
Serve the Kung Pao Eggplant with rice or noodles.