Start with sautéing the mushrooms and broccolini in 1 tsp of oil for about 5 minutes. Set it aside. In the same pan, add another tsp of oil add in the shrimp, minced garlic, a pinch of salt, red pepper flakes and pepper. Sauté for about 2 minutes each side. Place shrimp in a clean small bowl to the side.
In a medium bowl prepare the sauce ingredients by whisking together (soy sauce, vinegar, chili garlic, miso, peanut butter) it will be thick until you add the pasta water. Set aside until the pasta water is ready.
*don't forget to save your pasta water before draining the pasta!*
Gather the pasta water, add 1/3 cup of it to the miso sauce. Whisk it well. Keep a little extra pasta water to the side in case you need it once you combine everything.
In the same frying pan/wok used for the shrimp, wipe it with a paper towel and reheat it on medium/high heat. Add 1 tsp oil to the pan, followed by the cooked/drained noodles to the hot pan. Next, add in shrimp and veggies. Working quickly, pour in the miso sauce over everything and quickly toss and stir to evenly coat everything for about 1 minutes.
Don't let it reheat too long, the peanut butter will get a little chalky if you over cook it. *This is where you may need a little more pasta water to help spread things out.
Serve the miso noodles and add green onion garnish. Enjoy!