2 (3-inch) pieces ginger, cut in half lengthwise
2 onions, peeled
5 pounds beef marrow or knuckle bones
2 pounds beef chuck, cut into 2 pieces
2 scallions, cut into 4-inch lengths
1/3 cup fish sauce
2 ½ ounces rock sugar, or 2 1/2 tablespoons granulated sugar
8 star anise
6 cloves
1 cinnamon stick
1 black cardamom pod (optional)
2 teaspoons fennel seeds
2 teaspoons coriander seeds
1 tablespoon salt
1 pound dried pho noodles
1/3 pound beef sirloin, slightly frozen, then sliced paper-thin against the grain