Heat the oil in a large wok or saucepan over medium heat. Add the shallots and lemongrass and cook, stirring, until the shallots become translucent, for about 2-3 minutes. Add the mushrooms and cook, stirring often, for about 5-6 more minutes.
Add the bok choy, chile and cook, until the bok choy begins to wilt, about 1-2 minutes. Add the coconut milk, mirin, soy sauce, lime zest and a dash or two of red chili pepper flakes (if adding) and bring to a simmer. Cook until the sauce thickens, for about 3-5 minutes.
While your sauce is cooking these last 3-5 minutes, cook your noodles according to package directions. Drain and rinse.
To assemble: divide the noodles into bowls, top with the coconut sauce and vegetables. Garnish with the fresh cilantro, basil leaves, green onions, roasted sesame seeds, some lime juice and sriracha (if using). Mix and enjoy!