Place the dried ginger, cinnamon sticks, star anise and cloves in cheesecloth to create a sachet. Tie the ends of the cheesecloth together and set aside.
To a large stockpot, add the bones, onions, carrots, fresh ginger and salt, then cover with cold water.
Add the sachet of dried ingredients, bring to a rolling boil and skim any foam that develops.
Decrease the heat to simmer and cook for 1 hour—occasionally skimming foam.
After an hour, add the sugar, kosher salt and fish sauce and simmer for another 2 hours—continuing to skim frequently.
After 2 hours, add more water to bring the total volume to 15 quarts, cover the pot, decrease the heat to low and let the broth cook overnight.
After the broth has cooled, strain it through a fine strainer.
Add cooked beef, rice noodles and fresh herbs to make pho, or use the broth in other soups. It will keep for up to 5 days in the refrigerator or 6 months in the freezer.