Boil the noodles according to the package directions. Once finished, drain but reserve ½ cup of the pasta water.
In a large skillet, heat the olive oil over medium-high heat, and add the shallots, garlic, and mushrooms. Season with salt, pepper, and red pepper flakes. Cook the mushrooms for about 7 to 10 minutes, tossing occasionally until they turn color and release their juices.
Add the miso and stir until it is incorporated into the mushrooms
Add the cooked pasta, ½ to ¾ cup of the pasta cooking water, and the pesto to the mushrooms. Toss to combine. If needed add a little bit more of the pasta cooking water.
Notes
Don't forget to reserve that pasta water to add to the sauce! The salty, starchy pasta water not only adds flavor but helps glue the pasta and sauce together.
Pesto goes best with most curly pasta shapes! I like making it with fusilli but in a pinch, I also recommend, Bucatini, Capellini, thinner Spaghettini, and Fettuccine.
Don't ever rinse your pasta after draining! The pasta will be covered in starch that will help to emulsify the sauce and get it to stick better to the pasta.