How to Make It
In a large pot, cover the ribs, apple, garlic, ginger and onion with 3 quarts of water and bring to a boil over high heat, then simmer over moderately low heat until the ribs are very tender and the liquid is reduced by half, about 2 hours. Transfer the ribs to a work surface and let cool slightly, then cut the rack into individual ribs.
Strain the broth through a fine-mesh sieve into a heatproof bowl, discarding the solids. You should have 6 cups of broth; add water if needed. Return the broth to the pot and stir in the fish sauce, dashi and five-spice powder. Bring to a simmer over moderately high heat, then keep warm over very low heat.
Meanwhile, in a large baking dish, cover the noodles with boiling water and let stand until softened, about 20 minutes. Drain well.
In a large saucepan of salted boiling water, blanch the Broccolini until crisp-tender, about 2 minutes. Drain well; pat dry.
Transfer the noodles to 4 bowls and ladle the broth over them. Top with the ribs and Broccolini. Serve with thinly sliced scallions and jalapeño, as well as mint, basil and cilantro leaves.