Tonkotsu Ramen

Prepare the stock: Place chicken bones, pork bones, trotter, scallions, and ginger in a large stockpot; cover with cold water, noting water level in stockpot. Bring to a rapid boil over high, skimming off and discarding any foam and scum that rises to the surface. Boil for at least 6 hours or up to 16 hours, replenishing water to original level every hour or so. Allow stock to reduce without replenishment during final 1 hour of cooking, letting stock reduce to roughly 2 quarts (this may take up to 2 hours). Remove stock from heat; stir in kombu and let cool at room temperature for about 1 hour. Pour stock through a coarse mesh strainer into a large bowl; then pour stock through a fine mesh strainer into a separate large bowl, discarding solids. Cover and refrigerate until stock is fully gelatinized, about 12 hours.

Meanwhile, prepare the chashu pork: Heat a Dutch oven with a tight-fitting lid over medium-high; add oil. Add pork and sear until golden brown on at least 2 sides, about 3 minutes per side. Transfer pork to a plate and set aside. Reduce heat to medium; add garlic, scallions, ginger, and chile; cook, stirring often, until aromatic, about 1 minute. Carefully add mirin, sake, shoyu, rice wine vinegar, and brown sugar, stirring until sugar dissolves, about 30 seconds. Return pork to Dutch oven, nestling it among ingredients. Bring mixture to a simmer over medium; reduce heat to medium-low. Cover Dutch oven tightly with lid; simmer pork, flipping and basting every 30 minutes, until pork is tender enough to easily yield to a poke from a chopstick and a thermometer inserted into thickest portion registers 180°F, 1 to 1 1/2 hours. If a lot of cooking liquid evaporates during cooking process, add just enough water to keep bottom of Dutch oven covered. Let chashu cool in its cooking liquid at room temperature, about 1 hour; cover (still in its liquid) and refrigerate 12 hours.

While chashu chills, prepare the pickled mushrooms: Bring water in a medium saucepan to a boil over high. Remove from heat and stir in mushrooms; cover and let soak until mushrooms are softened and doubled in size, 15 minutes. Drain mushrooms and thinly slice. Place mushrooms in a heatproof container. Bring rice wine vinegar, shoyu, 1/4 cup water, and grated ginger to a boil in a small pot over high. Pour vinegar mixture over mushrooms and let cool to room temperature, about 1 hour. Cover and refrigerate 12 hours.

Prepare the ramen: Remove pickled mushrooms from refrigerator and let come to room temperature, about 30 minutes. Meanwhile, prepare noodles according to package directions.

While noodles cook, skim congealed fat from top of stock using a spoon; reserve fat for another use. Place stock in a medium pot and bring to a simmer over medium. Add shoyu, mirin, rice wine vinegar, and sesame oil, stirring to combine; season with salt to taste. Reduce heat to medium-low and simmer until ready to serve.

Remove chashu from cooking liquid, reserving liquid for another use. Cut pork into 1/4-inch slices. Working in 3 batches, heat a large skillet over medium-high; add 1 tablespoon of the oil. Place pork slices in a single layer in skillet and cook until browned, about 1 minute per side; set aside.

Add bok choy, cut side down, to skillet and cook, undisturbed, until browned, about 1 minute. Add water; cover skillet, steaming bok choy until vibrant green and slightly softened, about 2 minutes.

Ladle about 2 cups of hot stock into each of 4 warm bowls. Drain noodles and divide evenly among each bowl, arranging noodles neatly. Gently arrange 2 bok choy halves in each bowl; fan 3 to 4 chashu slices on top of noodles. Top each bowl with about 1/4 cup pickled mushrooms and 1 egg; place 1 nori sheet behind toppings. Serve immediately with chile oil on the side, if desired.