First, add the chopped green chilli to the vinegar and let it sit for atleast 15 mins. We will use this vinegar dip while serving the noodles. Also, clean the mushrooms nicely and slice them. Keep aside.
Boil a pot of water. Add the noodles to the boiling water and cook for about 3-4 mins until done. Once cooked, drain the water from the noodles. Add 1 tsp of oil to the noodles. Toss the noodles so that the oil coats the noodles. Keep aside.
Heat a pan / wok in medium heat with the remaining 3 Tbsp of oil. Add the white portion of the spring onion, ginger and garlic and saute until translucent.
Add the red chilli flakes, soy sauce, sriracha, salt to the pan and mix well.
Now, Add the sliced mushrooms to the pan and stir fry. Turn the flame to medium-low and cook until the mushrooms are cooked fully.
Once the mushroom is cooked fully, add the cooked noodles to the pan. Toss well until combined. Turn off the flame. Garnish with the green portion of spring onion and toasted sesame seeds.
Serve the hot noodles with the vinegar dipping or green chilli sauce and chili oil