First of all, press the tofu to remove the excess water. You can do it by wrapping the tofu in a kitchen towel and put a heavy object on top for around 20 minutes. Cut the tofu into 1-inch cubes.
Put a tablespoon of vegetable oil in a pan over medium-high flame. Add the tofu cubes and cook then until golden brown on each side, it may take around 5-7 minutes. Remove the tofu from the pan and keep it aside.
In the same pan, add the remaining tablespoon of vegetable oil.
Add the diced eggplant and cook until soft, it may take around 5-7 minutes.
Move the eggplant to the side of skillet. Add grated ginger and minced garlic and cook for around a minute until fragrant.
Put the cooked tofu to the skillet. Mix in the red bell pepper slices.
In a little bowl, mix the hoisin sauce, soy sauce, sesame oil, rice vinegar and red pepper flakes. Pour the sauce over the eggplant and tofu mixture.
Mix in the cornstarch mixture. Cook by stirring consistently, until the sauce becomes thick and it evenly coats the eggplant and tofu.
Take off the skillet from the heat. You can serve it hot over cooked rice by garnishing it with sesame seeds, green onion and fresh cilantro.