For the marinade: Put the eggplant in a large mixing bowl, then add the cornstarch, mirin and soy sauce and toss together until fully coated. Set aside.
For the sauce: Add the soy sauce, vinegar, sugar, cornstarch, ginger and garlic to a small mixing bowl, then whisk to combine.
For the stir-fry: In a wok or large skillet, melt 1 tablespoon coconut oil over high heat. Add the eggplant with its marinade and cook until lightly golden brown and tender, about 8 minutes, deglazing the pan if bits of food get stuck on by adding 1/4 cup water, wine or broth and stirring the bits up with a wooden spoon. Transfer the cooked eggplant back to the large mixing bowl and set aside.
Turn heat down to medium-high. Add the remaining tablespoon coconut oil to the pan; add the dried chiles and cook, stirring, until fragrant, 1 to 2 minutes. Add the bell pepper and cook until just tender, 5 to 7 minutes. Add the cooked eggplant, peanuts, scallions and sauce and toss to coat. Cook until the sauce is thickened, 1 minute.
Serve immediately with brown rice and scallions, for garnish.