How to Make It
In a small heatproof bowl, soak the dried shiitakes in 2 cups of boiling water until softened, about 30 minutes. Remove the shiitakes and finely chop. Pour the soaking liquid into a clean bowl, stopping before you reach the grit at the bottom.
In a large skillet, melt the butter. Add the shallot, garlic and ginger and cook over moderately low heat, stirring, until softened, about 3 minutes. Stir in the black bean sauce and wine. Add the fresh mushrooms and reconstituted shiitakes along with the reserved soaking liquid and 1 cup of water and cook, stirring occasionally, until the mushrooms are softened and saucy, about 15 minutes. Stir in the oyster sauce and season with salt. Scrape the ragù into a large bowl and keep warm. Clean the skillet.
In a large saucepan of salted boiling water, cook the spaghetti until al dente. Drain well.
Using the flat side of a chef’s knife, mash the garlic to a paste with a pinch of salt. In the skillet, heat the oil. Add the garlic paste and cook over low heat, stirring, until very fragrant and light golden, 3 minutes. Stir in the 2 tablespoons of scallions, the oyster sauce, Maggi sauce, black bean sauce and vinegar; warm over low heat. Add the spaghetti and toss to coat. Stir in the 1/4 cup of cheese and the butter and toss well. Transfer to plates and top with the mushroom ragù. Garnish with more cheese and scallions and serve.