Rice Noodles with Chinese Broccoli and Shiitake Mushrooms

Name: Rice Noodles with Chinese Broccoli and Shiitake Mushrooms
Ingredients: 8 ounces wide (about 3/8 inch) or other rice noodles; 12 ounces Chinese broccoli (also called gai lan), cut into 2-inch pieces; 3 tablespoons low-sodium tamari soy sauce; 1 tablespoon plus 1 teaspoon Thai fish sauce (also called nam pla); 1 tablespoon plus 1 teaspoon rice-wine vinegar (not seasoned); 1 teaspoon sugar; 3/4 cup homemade or low-sodium store-bought chicken stock; 1 tablespoon canola oil; 1 tablespoon minced peeled fresh ginger, or more to taste; 2 garlic cloves, minced; 8 shiitake mushrooms, stemmed, caps quartered; 2 teaspoons cornstarch mixed with 2 tablespoons cold water; 4 scallions, white and pale-green parts only, cut on the diagonal into 1-inch pieces; 2 teaspoons toasted sesame oil; Crushed red-pepper flakes, for sprinkling (optional); Sesame seeds, for sprinkling (optional); Coarse salt, for sprinkling (optional)