Cut your chicken into parts, and place them into a large pot and cover with cold water. Add the ginger slices and spring onion stalks.
Bring to a rolling boil. You will see grey/brown foam (impurities) rise to the surface. Let it boil for about 5 minutes.
Discard the boiling water. Rinse each piece of chicken under cold running water, scrubbing away any clotted blood or dark bits from the bones.
Return the cleaned chicken to a clean pot. Add 2.5 liters of water, the onion, garlic, white peppercorns, kelp, and bay leaves.
Bring to a boil over high heat. Once boiling, reduce to medium heat and cook for 15 minutes.
Lower the heat to low, cover with a lid, and let it gently simmer for 2 hours. The meat should be falling off the bone by the end of this window.
Use tongs to remove the kelp, bay leaves, and larger chicken bones.
Use a hand-held immersion blender directly in the pot. Blend the softened onions, garlic, and the remaining chicken meat into the liquid.
Cover the lid and continue to cook the blended broth on low for another 30 minutes. This allows the fats and proteins to fully integrate.
Set a fine-mesh strainer lined with cheesecloth over a large bowl or a pot.
Use a ladle to scoop the broth through the cheesecloth, and press down on the remaining pulp to extract every drop of flavor.
Let it cool completely, then transfer the chicken broth into a clean bottle or airtight container. It will keep well in the fridge for up to a week.
For longer storage, pour the broth into a silicone ice tray and freeze in portions. Once frozen, you can pop them out and store them in a freezer bag; this way, you can easily use just what you need. The broth will keep for up to 3 months in the freezer.
