Heat 1/2 tablespoon olive oil in a large, high-walled skillet over medium heat. Add the finely diced yellow onion and crushed garlic. Cook, stirring for about 5 minutes until softened and fragrant. Set the mixture aside to cool completely before using in the meatball mixture.

In a large bowl, combine the panko breadcrumbs, grated Parmesan cheese, whisked egg, milk, cooled onion and garlic from Step 1, salt, dried oregano, ground allspice, ground nutmeg, and black pepper. Gently fold in the ground pork and ground beef until just combined, being careful not to overwork the mixture. Shape into 1 1/2-inch meatballs and place on a plate. Chill in the refrigerator for at least 15 minutes (or up to overnight) to help them hold their shape.

While the meatballs chill, combine the beef broth, chicken bouillon cube, Worcestershire sauce, Dijon mustard, and dried parsley in a large measuring cup or bowl. Stir well and set aside.

Heat the remaining 1 1/2 tablespoons olive oil in a large skillet over medium-high heat. Brown the chilled meatballs in batches, making sure not to crowd the pan so that you can rotate them easily. Cook for about 1 minute per side until nicely browned on all sides. Remove the browned meatballs and set aside. Drain any excess oil from the skillet if needed.

Melt the unsalted butter in the same skillet over medium heat, using a spatula to scrape up any browned bits. Stir in the all-purpose flour and cook for about 2 minutes, stirring continually until it begins to turn golden brown. Gradually add the prepared beef broth mixture from Step 3 in small splashes, mixing constantly to prevent lumps. Bring the sauce to a boil, then reduce to a simmer. Place the sour cream in a medium bowl and stir in about 1/4 cup of the hot sauce to temper it. Add the tempered sour cream back into the skillet and stir to create a creamy consistency, keeping the heat low so the sauce stays smooth. I like to use this tempering method to avoid curdling the sour cream—it makes the gravy extra silky.

Return the browned meatballs, along with any accumulated juices, to the skillet with the gravy. Spoon the sauce over the meatballs, then cover the skillet partially and let everything simmer gently over low heat for 10-15 minutes, or until the meatballs are cooked through. Serve the Swedish meatballs hot, garnished with a sprinkle of fresh parsley if desired. They’re perfect over mashed potatoes or egg noodles.