Cook the pasta in boiling water until al dente, following the package instructions. Before draining, set aside a small cup of the pasta water. Then drain the pasta and set it aside.
Cook the salmon fillets by first patting the skin dry with a paper towel. Heat a little cooking oil in a pan over medium-high heat. Place the salmon skin-side down and cook for 5 minutes, then flip and cook the other side for another 3 minutes.
Heat 2 tablespoons of cooking oil in a pan. Add the shallot, lemongrass, fresh chili, kaffir lime leaves, and galangal. Stir and let them simmer until fragrant.