Tonkotsu Broth Recipe

Prep the bones

Rinse the pork bones and trotters under cold running water to remove surface blood and debris. Place bones in a large stockpot and cover with cold water (about 5 liters).

Blanch to remove impurities

Bring the pot to a rolling boil over high heat. Boil for 10–15 minutes until foam and scum rise. Skim and discard scum. Drain bones and rinse thoroughly under cold water, scrubbing any remaining blood or residue; rinse the pot as well.

Roast aromatics (optional)

Heat 1 tablespoon oil in a skillet over medium heat. Add halved onion, smashed ginger, and crushed garlic and lightly brown—about 3–4 minutes—to develop flavor. You may also char them directly over a gas flame for a slightly smokier note.

Combine for long simmer

Return cleaned bones to the large stockpot. Add the browned aromatics, green onion whites, and kombu if using. Pour in the additional 6 liters of cold water (or enough to cover bones by 2–3 inches).

Initial gentle boil then lower to a vigorous simmer

Bring the pot to a boil uncovered over high heat. Once it reaches a vigorous boil, lower heat to maintain a steady, vigorous simmer (not a gentle simmer) — the classic tonkotsu method relies on rolling agitation to emulsify marrow and collagen into a milky broth. Skim foam occasionally for clarity, but some emulsified fat and tiny particles are desirable.

Long simmer for emulsification

Simmer vigorously, uncovered, for 6–12 hours. Check water level every 30–60 minutes and top up with boiling water as needed to keep bones submerged. Stir or rock the pot gently every 20–30 minutes to promote bone-on-bone contact and release collagen. If using a pressure cooker or large slow cooker capable of high agitation, you can reduce time (pressure cooker: 2–3 hours high pressure).

Remove kombu and aromatics

In the last 15–20 minutes, remove kombu (it can make broth bitter if left too long). Remove larger aromatics like onions and green onions with tongs, squeezing gently to release collected juices back into the pot.

Strain the broth

Carefully ladle or pour the broth through a fine-mesh sieve or chinois into a clean container to remove bones and solids. For a silkier texture, line the sieve with cheesecloth and strain a second time.

Skim fat (optional) and cool

Allow the strained broth to sit until slightly cooled. If you want a less fatty broth, refrigerate until fat solidifies on top, then remove. For authentic tonkotsu, leave moderate fat for mouthfeel and flavor.

Finish seasoning

Reheat strained broth to serving temperature. Taste and add salt (start with 2–3 tsp), 2 tablespoons light soy sauce, mirin if using, and white pepper. If the broth tastes too intense or too thick, thin with up to 1 cup of chicken or vegetable stock or hot water until desired balance is reached.

Adjust and serve

Simmer 5–10 minutes to marry flavors. Adjust salt and soy as necessary. Use the finished tonkotsu broth as base for ramen bowls: place cooked ramen noodles in bowls, ladle hot broth over, and top with your preferred tare, chashu, soft-boiled egg, menma, negi, and nori.