Preheat oven to 375˚F.
Yellow curry paste: Place shallots, garlic, ginger, and lemongrass over a sheet of foil and drizzle with oil and lightly season with salt.
Wrap foil into a tight bundle, place directly onto a rack in the oven and lightly roast ingredients for 15 minutes. Remove from heat, open bundle and transfer to a food processor. Allow mixture to cool, about 10 minutes.
Add remaining paste ingredients into the food processor and pulse 6 to 8, times before fully pureeing until mixture is thick and smooth. Set aside.
Fill a large pot with water and bring to a boil over high heat. Add noodles and boil until cooked through, 4 to 5 minutes. Drain, rinse with a little cold water and set aside.
In the same pot heat oil over medium-high heat. Add mushrooms and sauté for 3 to 4 minutes.
Lower heat to medium and add a third of the curry paste (place remaining paste in an airtight container and refrigerate for up to 2 weeks). Toast paste with the mushroom for 1 to 2 minutes.
Stir in coconut milk until mixture is smooth and bring to a simmer. Stir in fish sauce (or mushroom sauce) and lime juice and simmer for 5 minutes.
Add noodles and toss together until fully coated. Simmer for an additional 2 to 3 minutes.
Adjust seasonings, if needed, top with cilantro and serve.