Singapore Shellfish Soup

2 tablespoons vegetable oil, divided

1 pound large raw shrimp, peeled, shells reserved

1 pound mussels, cleaned and debearded

3 stalks lemongrass, outer layers removed, inner core thinly sliced

3 serrano chilies, seeded and chopped

2 cloves garlic, minced

1 (1-inch) piece ginger, peeled and chopped

4 small shallots, peeled and sliced

1 tablespoon anchovy paste

1 teaspoon turmeric

1 tablespoon ground coriander

1 (14-ounce) can coconut milk

1–2 tablespoons fish sauce

1 7-ounce package of rice noodles, soaked in hot water until soft

1 tablespoon lime zest

6 large scallops, sliced horizontally into 2–3 pieces, depending on their size

1 cup bean sprouts

¼ cup chopped cilantro

Lime wedges