In a large bowl, use your fingers to mix the ground beef and ground pork with the chopped onion, garlic, bread crumbs, egg, milk, allspice, kosher salt and black pepper until combined.
Use a 1 tablespoon measuring spoon or #40 scoop to portion out the meatball mix. Lightly toss the meatball between the palms of your hand to form small, round balls. Place on a platter or baking sheet and repeat with the remaining mixture. Cover and refrigerate for 1 hour to help them hold their shape while cooking.
Preheat the oven to 375°F and remove the meatballs from the refrigerator.
Heat the canola oil in a large cast-iron or non-stick skillet over medium-high heat. Add half of the meatballs and fry for 1-2 minutes. Shake the pan so the meatballs turn and cook, repeating until they are lightly browned on all sides, a total of about 5 minutes. Transfer to a platter and repeat with the remaining meatballs. Add all of the meatballs back to the skillet and bake in the oven for 20-25 minutes or until the meatballs are cooked through with an internal temperature of 160°F.
While the meatballs are baking, make the Swedish cream sauce and prepare the noodles.
To make the noodles, bring a large pot of water to a boil, season with kosher salt, and add the pappardelle pasta. Cook for 9 minutes, drain and return the noodles to the pot (off the heat) with the butter, parsley, kosher salt, freshly ground black pepper. Stir, then cover with a lid until ready to serve.
To make the creamy sauce, melt the butter in a medium saucepan or high-sided skillet over medium heat. Whisk in the flour and cook for 1 minute or until it is lightly browned. Add the beef stock and whisk until smooth. Cook until the sauce thickens, about 3-4 minutes. Reduce the heat and stir in the cream, soy sauce and Dijon mustard and simmer for another 1-2 minutes. Taste for seasoning. If the sauce seems too thick, add more beef stock 1-2 tablespoons at a time.
Pour the sauce into the pan with the meatballs and stir to combine. Serve over the warm noodles and enjoy.