Make the meatballs: Put the breadcrumbs in a large bowl. Heat the butter in a skillet over medium heat. Add the onion, garlic, allspice, 2 teaspoons salt and 1/4 teaspoon white pepper and cook, stirring, until soft, about 5 minutes. Add the milk and Worcestershire sauce and bring to a simmer. Pour the milk mixture over the breadcrumbs and stir to make a thick paste; let cool. Add the beef, pork, egg and egg white to the bowl and mix until combined. Brush a baking sheet with vegetable oil. Roll the meat into 1-inch balls and arrange on the prepared baking sheet. Cover with plastic wrap and refrigerate at least 1 hour. Preheat the oven to 400 degrees F. Bake the meatballs until cooked through, about 20 minutes. Make the gravy: Melt the butter in a large skillet over medium heat. Add the flour and cook, whisking, until smooth. Whisk in the beef broth and Worcestershire sauce and bring to a simmer. Add the cream and meatballs. Reduce the heat to medium low and simmer until the gravy thickens, about 10 minutes. Season with salt and black pepper. Transfer to a serving dish; sprinkle with the parsley and serve with lingonberry jam, if desired.