Preheat oven to 450°F.
Place salmon fillets on a plate or work surface.
Brush each piece of salmon with 1 teaspoon sesame oil. Season, to taste, with salt and white pepper.
Place salmon fillets on 4 sheets of parchment paper or heavy foil.
Sprinkle ginger slices and white parts of scallions over fish.
Fold parchment or foil around fish to make an envelope or package for steaming fish.
Place in a rimmed baking (casserole) dish.
Place in preheated oven and bake for about 8 minutes or until salmon is barely opaque in center.
While salmon is cooking, place vegetable oil in a large skillet. Place over high heat and heat until very hot but not smoking.
Carefully add mushrooms, asparagus and bok choy. Stir-fry for about 2 - 3 minutes, until veggies are crisp-tender.
Add tomatoes. Stir-fry until just hot.
Transfer vegetables to serving platter or 4 individual serving plates.
Remove pan from oven. Carefully open packages. Be careful of the very hot steam escaping.
Place salmon fillets on top of vegetables.
Combine sauce ingredients, sugar, soy sauce and chicken broth in a microwavable bowl. Heat sauce.
Pour sauce over salmon and vegetables.
Garnish with green parts of scallions.
Serve immediately, hot.