Prepare noodles according to package instructions.
In a POT, heat 2 tbsp oil. Fry the spice paste for 2 minutes over medium-low heat, stirring constantly.
Add broth, coconut milk, bean sprouts, and shrimp.
Bring to a boil. Cook 5 minutes.
Add chilies to taste (opt.) and 1/4 cup lime juice or more to taste.
Adjust saltiness to taste with tamari or soy sauce, and/or anchovy paste or fish sauce.