Place the chicken in a pot with 8 cups water (about 2 liters), 3 slices of ginger, and 1 onion. Simmer over medium heat for about 45 minutes, then season to taste. Shred or cut the chicken into bite-sized pieces.

Thinly slice the onion and soak in cold water to reduce sharpness. Chop the green onions.

Place the pho noodles in a bowl. If using dried noodles, boil them with a little salt and oil, then rinse with cold water. Add the chicken, onions, and green onions. Sprinkle with a little black pepper and pour in the hot broth.