1 tablespoon white miso paste  | 
                                                2 teaspoons mirin (sweet rice wine)  | 
                                                2 teaspoons rice vinegar  | 
                                                2 teaspoons low-sodium soy sauce  | 
                                                1/2 teaspoon sugar  | 
                                                1/2 teaspoon grated peeled fresh ginger  | 
                                                2 (6-ounce) skinless salmon fillets  | 
                                                1 teaspoon toasted sesame seeds  | 
                                                2 teaspoons dark sesame oil  | 
                                                1 teaspoon bottled minced garlic  | 
                                                1 (10-ounce) package fresh spinach  | 
                                                2 teaspoons low-sodium soy sauce  |