In a medium sized bowl combine 1 pound ground beef, 1 pound ground pork, 1/2 cup panko bread crumbs, 2 tablespoons parsley, 1/2 teaspoon ground allspice, 1/2 teaspoon ground nutmeg, 1/2 cup onion, 1/4 teaspoon garlic powder, 1/4 teaspoon pepper, 1 teaspoon salt, and 2 eggs. Mix until combined.
Roll into equal sized meatballs (original recipe makes about 24; number of meatballs can change depending on size preference and/or if you scaled the recipe). In a large skillet, heat 1 tablespoon olive oil and 1 tablespoon butter over medium high heat. Add enough meatballs to the hot pan so that there is space in between each of them (you will most likely have to cook them in batches). Cook, turning frequently, until brown on each side and cooked through. This should take about 8-10 minutes. Transfer to a plate and cover with foil. Continue cooking remaining meatballs until done, transferring to the foil covered plate.
To make the Swedish Meatball sauce:
Add 4 tablespoons butter and 3 tablespoons all-purpose flour to skillet and whisk until it turns brown. Slowly stir in 2 cups beef broth and 1 cup heavy cream. Add 1 tablespoon Worcestershire sauce and 1 teaspoon Dijon mustard and bring to a simmer until sauce starts to thicken. Add salt and pepper to taste.
Add the cooked meatballs back to the skillet and simmer over low heat for another 1-2 minutes. Serve over pasta, mashed potatoes, or rice.