Turn on the broiler. Add onion and ginger to a sheet pan. Broil for 10 mins until the outside is charred.

Rinse chicken quickly then remove giblets inside cavity.

In a large stockpot, bring water to a boil. Once boiling, add chicken, onion, ginger, sachet of pho spices, rock sugar, and fish sauce to the pot. Bring water back to boil then turn down the heat to a simmer for 1.5 hours, checking the broth and stirring occasionally. Add salt to taste.

Carefully remove the whole chicken and remove the meat from the bones. Shred the meat and discard the bones.

Cook vermicelli noodles according to the package. Pour hot broth over noodles and add shredded chicken and desired garnishes.