Sauté the onion and garlic. Heat 1 tablespoon olive oil in a large, deep skillet over medium heat. Add the onion and cook until softened, about 4–5 minutes. Add the garlic and cook for another 30–60 seconds. Transfer to a large mixing bowl and allow to cool slightly.
Make the meatball mixture. Add the panko, Parmesan, egg, milk, salt, allspice, nutmeg, oregano, and pepper to the bowl with the onion and garlic. Mix to combine. Add the ground turkey and gently mix just until everything comes together. Avoid overmixing, which can make the meatballs tough.
Shape and chill. Roll the mixture into approximately 2-inch meatballs and place them on a plate or baking sheet. Refrigerate for 15 minutes to help them hold their shape while cooking.
Prepare the sauce mixture. While the meatballs chill, whisk together the beef broth, soy sauce, and chicken bouillon. Set aside.
Brown the meatballs. Heat the remaining 1 tablespoon olive oil in the same skillet over medium-high heat. Working in batches if necessary, brown the meatballs for about 1 minute per side. They do not need to be fully cooked at this point. Transfer to a plate.
Make the roux. Reduce the heat to medium and melt the butter in the same skillet. Stir in the flour and cook for about 2 minutes, stirring continuously, until lightly golden.
Make the gravy. Slowly pour in the prepared broth mixture, a little at a time, whisking continuously to keep the sauce smooth. Bring to a gentle boil, then reduce the heat to medium-low and simmer until the sauce begins to thicken.
Make it creamy. Slowly whisk in the heavy cream until smooth and combined.
Finish the meatballs. Return the meatballs and any accumulated juices to the skillet. Spoon the sauce over the top, partially cover, and simmer over low heat for 10–15 minutes, or until the meatballs are fully cooked through to 165°F in the center.
Serve. Spoon the meatballs and creamy gravy over egg noodles, mashed potatoes, or rice. Finish with fresh parsley, if desired, and enjoy!