4 cans of Wily Everyday Chicken Broth
1 (3-pound) boneless pork belly, skin removed
1 tablespoon vegetable oil
1 cup sake
1/2cup tamari
½ cup granulated sugar
1 (3-inch) piece fresh ginger, peeled and thinly sliced
3 scallions, cut into 3-inch pieces
Place the pork belly on a clean cutting board and arrange it so the short side is facing you. Tightly roll the pork into a log. Using kitchen twine, tightly tie the pork at 1-inch intervals.
Heat the oil in a large saucepan over medium-high. Add the pork and cook, turning as needed, until golden all over, 12 to 15 minutes. Transfer to a clean cutting board, then discard the oil and wipe up any large bits from the saucepan.
Add the broth, sake, tamari, sugar, ginger, and 1 cup water to the saucepan. Bring to a boil over high, then return the pork to the pot along with the scallions. Reduce the heat to maintain a simmer and cover with an otoshi buta, drop lid, or cartouche. Cook, turning the pork once halfway through, until tender, about 2 hours. Remove from the heat and let the pork cool in the cooking liquid, then cover and refrigerate for at least 8 hours or overnight.
The next day, transfer the pork to a clean cutting board. Remove and discard the solidified fat from the cooking liquid, then strain the liquid through a fine-mesh strainer set over a bowl, discarding the solids. Store the chashu in an airtight container with its cooking liquid, refrigerated, for up to 5 days.
When ready to eat, remove and discard the twine, then thinly slice into rounds. Heat a large cast-iron skillet over medium-high and cook the rounds in batches, flipping once, until golden on both sides, about 4 minutes. Alternatively, heat 1 ½ cups of the strained cooking liquid in a large skillet over medium, add the slices, and cook until heated through, about 3 minutes. Slices can also go straight into ramen; they will heat through in the soup.