Mix together the miso, rice vinegar, soy sauce, and ginger. Reserve two tablespoons of the mixture and set aside. Let the salmon marinate in the remaining sauce for 30 minutes in the refrigerator. Keep the reserved marinade for the bok choy.

Preheat the oven to 350 degrees Fahrenheit. Take the salmon out of the marinade and arrange on a greased baking sheet together with bok choy. Brush the reserved marinade over bok choy and bake in the oven for 20 to 25 minutes. Garnish with sliced scallions and sesame seeds. Serve over brown or white rice.