Whisk together all of the marinade ingredients and pour about 1/3 into a re-sealable plastic bag. Add the salmon fillets and refrigerate for .
If your sesame seeds are un-toasted, add to a dry skillet and toast over medium high heat for 3-4 minutes, or until the sesame seeds are fragrant and begin to turn a golden color. Stay close and stir often.
Add sesame seeds to remaining marinade. Make a slurry with 1 tbsp corn starch and 1-2 tablespoons of the remaining marinade, combine with the rest of the marinade and pour into a small sauce pan. Heat over medium heat 2-3 minutes until the sauce thickens. Set aside until ready to use.
Slice 4 baby bok choy into halves or thirds, rinse under cold water, and thickly slice 4 oz or 10-12 shiitake or cremini mushrooms.
Spray a medium skillet with vegetable spray and heat over medium to high heat for 2-3 minutes or until the pan is very hot. Add the salmon, skin side up, and sear for 3-4 minutes on the first side.
Check once during the searing of the first side and then turn skin side down and sear for another 3-4 minutes, remove from skillet and set aside.
Add the marinade remaining from the salmon to the skillet, bring to a boil, reduce by half, and then add the sliced mushrooms.
Reduce the heat to medium, top the mushrooms with the bok choy. Cook over medium heat for one or two minutes, turning the bok choy in the pan a couple of times.