In a large bowl, combine the cubed bread and the 1/2 cup of milk. Let the bread soak in the milk for 10 minutes.
Heat 1 tablespoon of the olive oil in a large skillet over medium heat. Add the grated onion and saute for 5 minutes until softened and transparent. Remove from the heat and cool.
In the large bowl with the bread and milk, combine the ground beef, ground pork, egg, salt, pepper, nutmeg, and garlic powder along with the cooled onions. Mix with your hands until combined.
Form into roughly 25 meatballs and set aside on a baking sheet.
Heat the remaining olive oil and butter over medium-high heat in the same skillet that the onions were cooked in. Fit roughly 5-6 meatballs in the pan at once, cooking for 5 minutes while rotating to brown all sides. Remove from pan and set aside.
Once all of the meatballs are cooked, start making the sauce in the same pan you cooked the meatballs in.
Whisk in the flour and cook for about 2-3 minutes until light brown. Whisk in the beef broth, cream, Worcestershire sauce, salt and pepper. Bring to a simmer until sauce thickens. Roughly 3 minutes.
Add the meatballs to the sauce and reduce to medium-low heat. Simmer for 8-10 minutes to finish cooking the meatballs.
Add chopped parsley to the top, serve and enjoy!