How to Make It
Heat 1 tablespoon oil in a large skillet over medium-high. Add onion, garlic, 1 teaspoon salt, fennel seeds, black pepper, and red pepper; cook 10 minutes or until onion is very tender, stirring occasionally. Place onion mixture in a bowl; cool completely.
Tear bread into small pieces. Place onion mixture, bread pieces, beef, and pork in a large bowl; mix gently with your hands to combine. Shape beef mixture into 42 meatballs (about 1 1/2 tablespoons each). Reserve 2 of the meatballs. Arrange the remaining 40 meatballs on 2 large foil-lined baking sheets coated with cooking spray.
Broil meatballs for7 minutes or until browned and done. Reserve 24 meatballs for Ban Mi Bowls and Greek Stuffed Pitas.
Heat remaining 1 teaspoon oil in a saucepan over medium-high. Add 2 uncooked meatballs to pan; cook 4 minutes, stirring to crumble. Add flour and allspice; cook 1 minute, stirring constantly. Add remaining 1/4 teaspoon salt and stock; bring to a boil. Cook 10 minutes or until sauce is reduced to about 1 cup. Remove pan from heat. Stir in sour cream, butter, and vinegar. Spoon sauce evenly over meatballs. Sprinkle chopped dill evenly over top.