How to Make It
Preheat the oven to 400°. Coat a rimmed baking sheet with 1 tablespoon of the oil. Using a melon baller or a grapefruit knife, hollow out the tomato halves, leaving thin yet sturdy cups; reserve the scooped out tomato flesh in a bowl. Set the tomato cups on the prepared baking sheet.
In a large skillet, melt the butter in 1 tablespoon of the oil. Add the onion and garlic and cook over moderate heat, stirring occasionally, until softened but not browned, about 5 minutes. Add the ground pork and veal and season with the salt, pepper and nutmeg. Cook over moderately high heat, breaking up the ground pork and veal with a wooden spoon, until the meats lose their pink color, about 4 minutes; don't let them brown. Add the reserved tomato flesh to the skillet and cook until the juices evaporate, about 5 minutes.
Transfer the meat mixture to a bowl and let cool slightly. Beat in the parsley, eggs, 1/4 cup of bread crumbs and the Parmesan. Spoon the stuffing into the tomato cups, mounding it slightly. Sprinkle the remaining 1/2 cup of bread crumbs over the tomatoes and drizzle with the remaining 1 tablespoon of oil.
Bake the tomatoes for about 45 minutes, or until the sides are soft and the stuffing is hot throughout. Set 4 stuffed tomato halves on each plate and serve.