Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a large bowl, combine ground beef, ground pork, breadcrumbs, milk, egg, onion, garlic, Worcestershire sauce, salt, pepper, and nutmeg. Mix gently until just combined; do not overmix.
Shape the mixture into 1-inch meatballs and place on the prepared baking sheet.
Bake in the preheated oven for 20–25 minutes, or until meatballs are cooked through and no longer pink in the center.
While meatballs bake, melt butter in a large skillet over medium heat. Stir in flour and cook for 1 minute to make a roux.
Gradually whisk in beef broth, then add heavy cream and soy sauce (if using). Bring to a simmer and cook until slightly thickened, about 5 minutes.
Remove skillet from heat and stir in cooked meatballs. Simmer gently for 5 minutes to warm through and allow flavors to meld.
Serve hot, garnished with chopped parsley, alongside mashed potatoes or lingonberry jam if desired.
Notes
For best results, avoid overmixing the meatball mixture to keep them tender. The gravy can be made ahead and reheated when ready to serve.