Cook the ramen according to the package directions. Strain and rinse with warm water to remove excess starch. Set aside.
Cook Veggies. In a large pan, heat 2 tsp oil over medium high heat. When the pan is hot, add mushrooms and whites from onions. Cook for 3-5 min, until they start to soften. Add bok choy and continue cooking for 2-3 more min, until tender. Set aside on a plate.
Cook Chili-Garlic Oil. In the same pan, add 1.5 tbsp neutral-tasting oil, sesame oil, garlic, ginger and chili flakes. Cook over medium-low heat for 3-5 min, stirring, keeping an eye on the garlic so it doesnt burn. When the edges of the garlic start to turn golden brown, take it off the heat immediatly.
Mix Spicy-Miso Sauce. Off heat, in the pan with the chili-garlic oil, add miso paste, tahini and soy sauce. Whisk very well to combine. It won't be 100% emulsified yet - don't worry. Add 3-4 tbsp of water, whisking well to combine, until the sauce is emulsified and the texture of a creamy salad dressing.
Finish Noodles: To the pan with the sauce, add noodles and veggies. Cook over low heat, tossing, until the noodles are coated in the sauce and everything is heated through. Add more water if needed. Taste and add more soy or rice vinegar.
Serve noodles: Plate with green parts of onions sprinkled over. Great with sesame seeds, a soft-boiled egg (pictured) or poached egg (my personal fave), kimchi and extra hot sauce if you like.