Tonkotsu is a Japanese noodle soup characterized by its salty pork broth. The most traditional preparations are made by boiling pork bones, usually for 12 hours or more. Fast-cook or “instant” versions are also available, though these iterations often lack some of the richness of the more authentic — but time intensive — original. The dish is believed to have been first made on the southern Japanese island of Kyushu, but is popular throughout the country as well as at Japanese eating establishments throughout the world.
There are many different types of Japanese noodle soups, though tonkotsu is almost always prepared as a ramen. Ramen noodles are thin and starchy and are usually designed to float in a salty, savory broth in bunches or “nests.” The distinguishing feature of any tonkotsu is not the noodles as much as it is the broth, however.
Pork bones are required for traditional tonkotsu. Cooks usually begin with the freshest bones available, optimally with some fat and meat still attached. The bones must be slow boiled for hours. Most recipes require at least 10 hours, with some calling for up to 15. Boiling for this long ensures that all of the marrow has been released and creates a fragrant, thick broth.
Cooks normally filter the broth after it has boiled to remove any floating fat or particulates. The finished broth is usually milky white and opaque and typically tastes decidedly of pork. Noodles and other soup additions are added to this broth base.
Tonkotsu ingredients can vary from kitchen to kitchen. The simplest soups are little more than the pork bone broth, noodles, and a small garnish like chopped scallions or sliced mushrooms. Soy sauce is a common seasoning, particularly when slightly sweetened.
More involved preparations often include boiled egg, robust vegetable presentations, and sliced pork loin or pork fillet. In most cases, though, the quality of a tonkotsu is dictated more by its base broth than its toppings and additions. A number of cooks refuse to add more than scant seasonings to their creations for fear of masking or blurring the delicately balanced broth.
Not all consumers are so picky, and many tonkotsu-inspired ramen dishes are available in restaurants and to home cooks. These are usually marked by a pork broth that tastes reminiscent to a broth that has boiled with bones for hours, but it is usually based more on flavor extracts and seasonings than actual bone marrow or time-saturated taste. Japanese soups in this category often satisfy the cravings of tonkotsu ramen lovers without requiring the time or expense of the traditional preparation.