Preheat the oven to 300°F (150°C).
Wash the eggplants, then cut them in half lengthwise. Place them on a baking sheet and score the flesh in a crosshatched pattern, being careful not to cut through the skin. Drizzle with a generous amount of olive oil, and sprinkle liberally with salt and pepper.
Bake for 45-60 minutes, or until flesh is tender. Tent the eggplants with foil and let them rest for 15 minutes while you prepare the filling.
Heat a little olive oil in a skillet until hot, then sauté the onion, pepper, and garlic until softened. While the veggies are cooking, scoop out the flesh from each eggplant and add it to the pan.
When the vegetables are starting to brown, add the ground meat (or the vegetarian meat alternative) and sauté until cooked through. Season to taste with salt and pepper, then remove from the heat and let it rest for a few minutes.
To fill the skins, spread a layer of tomato sauce in the empty skins, then fill each one to the top with the meat mixture. Cover with grated mozzarella cheese.
Pop the tray of stuffed eggplants under the broiler until the cheese is browned on the top, then let them rest for about 10 minutes before serving. Enjoy while hot and fresh!