Coconut Noodles with Scallops and Pea Tendrils

1 (6.75-ounce) package uncooked rice sticks (rice-flour noodles)

1/2 cup chopped fresh cilantro

1/3 cup coarsely chopped peeled fresh lemongrass (about 2 stalks)

1 tablespoon grated peeled fresh ginger

2 teaspoons shrimp paste or anchovy paste

3 to 4 Thai chiles, halved and seeded

3 garlic cloves, peeled

2 shallots, peeled

1 tablespoon dark sesame oil

1 cup fat-free, less-sodium chicken broth

2 tablespoons brown sugar

3 1/2 tablespoons lower-sodium soy sauce

1/4 teaspoon salt

1 (14-ounce) can light coconut milk

4 cups thinly sliced napa (Chinese) cabbage (1 small head)

1 1/2 cups thinly sliced green onions, divided

1 cup fresh or frozen green peas, thawed

1 pound sea scallops, halved horizontally

4 cups pea tendrils, coarsely chopped (about 1/4 pound)