Preheat the oven to 400°F. Wash and dry the eggplants, then slice them in half lengthwise.
Scoop out the eggplant flesh, leaving a shell about 1/4-1/2 inch thick. Set the eggplant boats aside on a baking sheet. Discard any seeds, then chop the remaining eggplant flesh. You should have about 1-2 cups of chopped eggplant. Set it aside.
In a large skillet, heat one tablespoon of olive oil over medium heat. Add the chopped onion and sauté until it is softened, about 5 minutes.
Add the ground chuck to the skillet and cook until it is no longer pink, breaking it up as it cooks.
Add the chopped eggplant, salt, black pepper, and Italian seasoning to the skillet. Cook just until the eggplant has softened and absorbed some liquid, about 5 minutes.
Stir in the pasta sauce. Bring the mixture to a light simmer, then take it off the heat.
Spoon the mixture into the eggplant shells, dividing it evenly. Top each eggplant boat with the shredded mozzarella cheese.
Loosely cover the baking sheet with foil. Bake the stuffed eggplants for 30 minutes with the foil on.
Remove the foil and bake or broil for a few more minutes, or until the eggplants are tender and the cheese is melted and golden. Serve warm and enjoy!