1. In a large saute pan, heat 2 teaspoons olive oil over medium heat. Add onion and garlic, and saute until translucent, 3 to 5 minutes. Place the ground meats in a large mixing bowl. Remove onions from heat, and add to ground meats. Add egg, egg yolk, Parmigiano-Reggiano and 1/4 cup breadcrumbs to bowl, and combine. Season with salt and pepper. Add the red pepper flakes and oregano, and mix well to combine.
2. Roll the ground-meat mixture into golfball-size meatballs. Place on a baking sheet covered with bread crumbs, and roll. In a large skillet, heat 1/4 cup olive oil over medium heat. Add the meatballs, and brown on all sides, 3 to 5 minutes. Remove the meatballs from the pan to a baking sheet lined with paper towels, and discard the remaining oil. Return them to the pan, and cover with 3 cups tomato sauce. Slowly simmer over medium heat, until the meatballs are heated through, about 15 minutes.
3. Bring a large pot of salted water to a boil. Add the spaghetti, and cook until al dente, about 6 to 8 minutes, or according to package instructions. Drain, and add cooked spaghetti to the sauce mixture. Cook for an additional 2 minutes. Serve immediately.