Cook the spaghetti according to its package instructions, removing from the pasta water 1 minute prior to "al dente". Set aside.
Meanwhile, combine the beef, breadcrumbs, Parmesan, cream, egg, half the garlic and 1 tablespoon oregano in a large bowl. Sprinkle with salt and pepper. Using your hands or a wooden spatula, mix together until well combined. Portion into 10 meatballs. Set aside.
Heat the olive oil in a large skillet over medium-high heat. Brown the meatballs, turning as needed, until browned on all sides, 5 to 6 minutes. Move the meatballs to the edge of the skillet.
Reduce the heat to medium and add the onion to the center of the skillet, along with the remaining garlic and oregano. Cook to release the flavor, a minute or two. Add the tomatoes and crushed red pepper, along with 1/2 cup hot water. Season with a pinch of salt and pepper, then carefully stir the meatballs into the sauce. Simmer, allowing the sauce to reduce slightly and the meatballs to finish cooking, about 15 minutes. Taste and adjust seasoning as needed.
Add the pasta to the skillet and toss with the sauce, making sure to thoroughly coat the noodles in the sauce. Arrange the meatballs on top of the pasta and sprinkle the mozzarella on top, being careful not to completely cover the meatballs and sauce (so it looks pretty after baking) and transfer to the oven. Bake until bubbly and the cheese is completely melted, about 12 minutes.
Remove the skillet from the oven and top with Parmesan and the fresh basil. Serve straight from the skillet.