12 slices day-old white bread, crumbled
3 cups heavy cream
2 tablespoons butter
6 small onion, minced
4 pounds ground beef
2 pounds finely ground pork
6 egg
1/4 cup and 2 tablespoons brown sugar (optional)
2 tablespoons salt

1-1/2 teaspoons ground black pepper
1-1/2 teaspoons ground nutmeg
1-1/2 teaspoons ground allspice
3/4 teaspoon ground ginger (optional)
1/4 cup and 2 tablespoons butter
1-1/2 cups chicken broth
1 cup and 2 tablespoons all-purpose flour, or as needed
12 cups beef broth, or as needed
3 (8 ounce) containers sour cream

12 slices day-old white bread, crumbled 3 cup s heavy cream 2 tablespoons butter 6 small onion, minced 4 pounds ground beef 2 pounds finely ground pork 6 egg 1/4 cup and 2 tablespoons brown sugar (optional) 2 tablespoons salt 1 -1/2 teaspoons ground black pepper 1 -1/2 teaspoons ground nutmeg 1 -1/2 teaspoons ground allspice 3/4 teaspoon ground ginger (optional) 1/4 cup and 2 tablespoons butter 1 -1/2 cups chicken broth 1 cup and 2 tablespoons all-purpose flour, or as needed 12 cup s beef broth, or as needed 3 (8 ounce) containers sour cream

Preheat oven to 350 degrees F (175 degrees C).
Place the bread crumbs into a small bowl, and mix in the cream. Allow to stand until crumbs absorb the cream, about 10 minutes. While the bread is soaking, melt 1 teaspoon of butter in a skillet over medium heat, and cook and stir the onion until it turns light brown, about 10 minutes. Place onion into a mixing bowl; mix with the ground beef, ground pork, egg, brown sugar, salt, black pepper, nutmeg, allspice, and ginger. Lightly mix in the bread crumbs and cream.
Melt 1 tablespoon of butter in a large skillet over medium heat. Pinch off about 1 1/2 tablespoon of the meat mixture per meatball, and form into balls. Place the meatballs into the skillet, and cook just until the outsides are brown, about 5 minutes, turning the meatballs often. Insides of the meatballs will still be pink. Place browned meatballs into a baking dish, pour in chicken broth, and cover with foil.
Bake in the preheated oven until the meatballs are tender, about 40 minutes. Remove meatballs to a serving dish.
To make brown gravy, pour pan drippings into a saucepan over medium heat. Whisk the flour into the pan drippings until smooth, and gradually whisk in enough beef broth to total about 2 1/2 cups of liquid. Bring the gravy to a simmer, whisking constantly until thick, about 5 minutes. Just before serving, whisk in the sour cream. Season to taste with salt and black pepper. Serve the gravy with the meatballs.