Atsumori Tsukemen

Prepare the Dashi: Wipe kombu clean with a damp cloth. Place kombu in 1500g of water and let it soak for at least 30 minutes. Heat the water gently over medium-low heat. Just before it boils, remove the kombu. Bring the water to a boil, then turn off the heat and add katsuobushi. Let it steep for 5 minutes, then strain the dashi through a fine-mesh sieve, discarding the katsuobushi.

Prepare the Broth Base: Thoroughly rinse pork bones and chicken bones under cold water. Blanch the bones by placing them in a large pot, covering with cold water, bringing to a rolling boil for 10 minutes, then draining and rinsing the bones and pot to remove impurities. Return the blanched pork bones and chicken bones to the clean pot. Add 4000g of fresh water, 50g of the green part of scallions, 30g of ginger (sliced), and garlic. Bring to a boil, then reduce heat to a gentle simmer. Skim any scum that rises to the surface. Simmer for 8-10 hours, replenishing water as needed to keep bones submerged, until the broth is milky white and rich. Strain the broth, discarding solids.

Prepare the Chashu: Roll the pork belly tightly and tie it with kitchen twine to form a compact cylinder. Heat a large pan over medium-high heat and sear the pork belly on all sides until deeply browned. In a separate pot, combine 100g of koikuchi soy sauce, 50g of mirin, 50g of sake, 20g of sugar, 20g of ginger (sliced), 30g of the white part of scallions, and 300g of water. Bring to a simmer, then add the seared pork belly. Ensure the pork belly is mostly submerged; add more water if necessary. Cover and simmer gently for 2-3 hours, or until the pork belly is very tender. Let the pork belly cool completely in its braising liquid, then refrigerate overnight. Remove the pork belly from the liquid, untie, and slice thinly before serving.