In a medium sized bowl combine ground beef, ground pork, panko bread crumbs, parsley, allspice, nutmeg, onion, garlic powder, pepper, salt and eggs. Mix until combined.
Roll into 24 meatballs. In a large skillet, heat 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 flour to skillet and whisk until it turns brown. Slowly stir in beef broth and heavy cream. Add worchestershire sauce and 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.