If using a whole chicken, separate into chicken bones, boneless breasts and bone-in thighs and drumsticks. Slice the breasts into strips and use the poultry shears to cut thighs and drumsticks into smaller pieces.
Bring a large pot with plenty of water to a boil, then add the chicken bones (with the wings and legs too, if any) and parboil for 1-2 minutes. Discard the liquid and give the bones a quick rinse. Clean the pot.
Add 5 cups (1.2l) of water to the pot. Bring it to a simmer then add the chicken bones, ginger and 1 teaspoon salt. Let it come to a boil, then skim off the foam and return to a simmer.
Place a skillet over medium heat and dry roast the shallots for several minutes until they are lightly charred and yield to the touch. Add the shallots to the stock pot, then cover and simmer for about 1 hour or up to 1.5 hours.
Place a small pot over medium heat and add the oil. Place the annatto seeds in a heat-proofed bowl and once the oil is hot, pour it over the seeds. The oil should turn reddish and you can discard the seeds.
Toss the chicken breast strips with ½ teaspoon turmeric powder, 2 teaspoons fish sauce, ¼ teaspoon black pepper and ½ tablespoon red annatto oil. Set aside to marinate for 20-30 minutes.
Toss the chopped thighs and drumsticks with the remaining turmeric powder, 4 teaspoons fish sauce, ¼ teaspoon black pepper and 1 tablespoon red annatto oil. Set aside to marinate for 45-60 minutes.
Once the marinating time for the chicken breast is over, place a sauté pan over medium heat. Heat 1 tablespoon red annatto oil, then add ⅓ of the pounded Vietnamese pearl onions and cook for a few seconds until fragrant.
Add the chicken breasts and sauté until the outside is no longer pink. Add ¼ cup (40ml) water into the pan and braise for about 10 minutes until the meat firms up and absorbs the seasonings. Transfer the meat along with any cooking juice to a clean bowl.
Heat the remaining red annatto oil and sauté the remaining pounded Vietnamese pearl onions until fragrant. Add the chopped thighs and drumsticks and sauté until the outside is no longer pink. Then add 3/4 cup (180ml) water into the pan and braise for about 20 minutes (up to 30 minutes) until the meat firms up and absorbs the seasonings. Transfer the meat along with half of the cooking juice to a clean bowl. Pour the remaining cooking juice into the stock pot.
The broth should also be ready by now. Season the broth with 1-2 teaspoons fish sauce or to taste. The broth for mi Quang is usually heavily-seasoned.