Prep the chicken. Rinse the chicken under cold water and remove any excess fat or giblets. Pat it dry.
If using parts, keep them bone-in for the best flavor and body in the broth.
Build the base. Place the chicken in a large pot with onion, garlic, ginger, and the white parts of the scallions. Add enough water to cover by about an inch.
Bring to a gentle boil. Heat over medium-high until it starts to bubble. Skim off any foam that rises to the surface.
This helps keep the broth clean-tasting.
Simmer low and slow. Reduce to a gentle simmer, cover partially, and cook for 60–90 minutes. The meat should be very tender and the broth slightly cloudy from the collagen.
Remove and shred the chicken. Carefully lift the chicken out and let it cool slightly. Shred the meat into bite-size pieces, discarding skin and bones.
Keep it simple—no need to over-season here.
Strain the broth. Pour the broth through a fine-mesh strainer into a clean pot. Discard the solids. Return the clear broth to the stove.
Season thoughtfully. Add the shredded chicken back to the pot.
Season with salt and a few grinds of black pepper. If you like a touch more savoriness, stir in a splash of guk-ganjang or light soy sauce.
Garnish and serve. Ladle the soup into bowls over a scoop of hot rice. Top with sliced scallion greens and a few drops of sesame oil.
Let each person add extra salt and pepper to taste.