Bring a large pot of water to a rolling boil. Add the beef sinew and boil for 2 minutes to remove impurities. Drain, rinse under cold water, and repeat once more if the meat still smells strong. Cut the pre-boiled beef into 2 cm cubes.
Tear the konnyaku into rough bite-sized pieces with a spoon — the jagged edges hold the broth better. (For a neater look, cut into 2 cm cubes instead.) Put in a bowl, sprinkle with a good pinch of salt, and rub for 1 minute. Boil the salted konnyaku for 2 minutes and drain.
Peel the daikon and cut into 2 cm cubes to match the konnyaku.
Put beef, daikon, and konnyaku into the pressure cooker pot. Add ginger slices and the whole green scallion. Whisk sake, sugar, soy sauce, white miso, and water together in a bowl, then pour over the ingredients.
Lay a sheet of aluminum foil directly on top of the ingredients as an otoshibuta (drop lid), with a small hole poked in the centre for steam.
Close the lid and pressure cook on high for 15 minutes. Let the pressure release naturally — about 20–25 minutes.
Remove the foil, ginger, and green scallion. Switch to sauté mode and simmer uncovered until the broth reduces by a third and glosses the ingredients. Taste and adjust with more miso if needed.
Ladle into small bowls. Top with chopped scallion and a generous dusting of ichimi togarashi. Serve hot with rice.
