Place all the ingredients of the chili paste in a food processor. Process until extremely smooth. Can be stored in the refrigerator in an airtight container for up to 1 week.
Salt and pepper both sides of the salmon. Heat a large pan over medium-high heat. Place the salmon skin-side down and cook until the skin crisp up, about 5 minutes. Flip and allow the top to lightly brown. Transfer to a plate and set aside.
In the same pan, add the lemongrass and oyster mushrooms. Cook until the mushrooms start to crisp up. Remove the mushrooms and set aside.
Add the chili paste, vegetable broth, and coconut milk. Bring to a simmer and reduce the heat to medium. Add the salmon and cover. Cook for 8 minutes, or until the salmon registers an internal temperature of 145°F.
Remove the salmon and add the mushrooms back. Allow the mushrooms to warm back up. Add the fish sauce, lime zest, and lime juice.
To serve, place a portion of rice noodles in a bowl. Add a portion of the curry sauce. Top with a piece of salmon, cilantro, and scallions.