Start by gathering all your ingredients.

Preheat your oven to 400°F (200°C) and roast the chicken bones for 30 minutes.

In a large stockpot, combine the roasted chicken bones, onion, garlic, ginger, and green onions.

Add the water and bring to a boil over medium-high heat.

Once boiling, reduce the heat to low and simmer for at least 2 hours.

Periodically skim any foam or impurities that rise to the surface.

After simmering, stir in the soy sauce and mirin.

Remove the pot from heat and strain the broth through a fine-mesh strainer or cheesecloth.

Taste the broth and adjust seasoning with salt as needed.