To make Braised Pork Belly, cut pork into 1 1/2-inch cubes; remove excess fat. In large pot, combine pork, sake, soy sauce, orange juice, vinegar, honey, star anise, cinnamon and ginger; bring to a boil. Place a sheet of parchment paper directly onto surface of liquid; transfer pot to 300°F oven. Cook 2-3 hours or until pork is tender. Remove pork; refrigerate, covered. Strain braising liquid; chill and remove solidified fat.
To make Dashi Broth, in saucepan, bring 4 quarts water and kombu to a boil. Remove kombu immediately; add bonito flakes and boil 15 seconds. Strain through chinois or coffee filter. Add soy sauce, mirin and sake. Adjust seasoning to taste. (Yield: 24 cups)
For each serving, to order, heat 4 cubes pork in a little braising liquid. Heat 1 cup Dashi with 3 tablespoons pork braising liquid. Sauté 3 cups spinach in oil just until wilted; mound in shallow bowl. Arrange pork on top of spinach; pour broth around. (Broth may be added tableside, if desired.)
Recipe by Chef Sean O’Brien, Zinnia Restaurant (San Francisco)