While meatballs are cooking, prepare the sauce: Melt the butter in a large skillet.
Add the flour to the butter and whisk well. Cook over med-low heat until mixture turns a little darker. Whisk often.
6 tablespoons unsalted butter, ⅓ cup all-purpose flour, 14.5 ounces low sodium beef broth, 14.5 ounces low-sodium chicken broth, 1 cup heavy cream, ¾ cup sour cream, 1 teaspoon Beef Instant Bouillon Granules, 1 tablespoon low-sodium soy sauce, 1 teaspoon Dijon mustard, 1 teaspoon Worcestershire sauce, 1 teaspoon apple cider vinegar, 1 tablespoon granulated sugar, ½ teaspoon freshly ground black pepper, Kosher salt, 1-2 tablespoons minced fresh parsley
Add beef broth, chicken broth, cream, sour cream, soy sauce, Dijon mustard, Worcestershire sauce, cider vinegar, sugar and black pepper. Taste, then season with salt, if needed.
Bring to a boil over medium heat, then reduce heat to low and add the meatballs. Simmer, stirring gently and often, until gravy has thickened. Add chopped parsley and stir gently.
Serve over egg noodles, mashed potatoes, or macaroni. If eating Swedish Meatballs without noodles or a side dish, serve with a teaspoon of cranberry sauce or lingonberry jam on the side, optional.
Cranberry sauce