Make the Meatballs. In a large bowl, combine ground beef, ground pork, breadcrumbs soaked in milk, egg, onion, and seasonings. Mix gently with your hands, then roll into 1-inch balls.
Brown the Meatballs. In a skillet over medium heat, brown the meatballs in batches. Don’t cook them all the way through—just enough to form a crust. This adds flavor and helps them hold their shape in the slow cooker.
Prepare the Sauce. In the same skillet, melt butter and whisk in flour to create a roux. Slowly add beef broth and Worcestershire sauce, whisking constantly until smooth. Transfer to the crockpot.
Slow Cook. Place the browned meatballs in the crockpot with the sauce. Cover and cook on low for 4–5 hours or on high for 2–3 hours.
Stir in Creams. 30 minutes before serving, stir in the heavy cream and sour cream. Let it warm through and thicken slightly before serving.
Garnish and Serve. Sprinkle with chopped fresh parsley and serve over buttery egg noodles, mashed potatoes, or even rice. Don’t forget a side of lingonberry jam for a sweet-tart contrast that’s totally traditional!