Whisk together ingredients for sauce, and set aside.
Pat dry salmon fillet, and cut into large chunks.
Slice red onion into half moons.
Peel and mince garlic cloves.
Peel and grate ginger until you have about one tablespoon.
De-seed bell peppers, then cut into bite-sized chunks.
Wipe any dirt off mushrooms, then cut into quarters (or eighths if mushrooms are very large).
Heat 1 tablespoon vegetable oil in a 12-inch nonstick skillet or wok over medium-high heat, then add salmon.
Let salmon pieces cook, without stirring, until bottoms are lightly browned, about 4 minutes.
Flip pieces over carefully and cook until the opposite sides are lightly browned as well, about 3 minutes. Salmon should be just barely cooked through. Remove from pan and set aside.
Add mushrooms to the pan. Sauté until mushrooms begin to brown, about 3 minutes.
Push the mushrooms to the sides of the pan and add ½ tablespoon oil to the middle of the pan.
Add the broccoli florets. Stir together, then cover and cook for 2 minutes.
Remove cover, stir, then clear a space in the middle of the pan.
Add ½ tablespoon of oil, then add onions, garlic, ginger, and peppers to the pan.
Stir together and sauté for 5-7 more minutes, until vegetables are tender and starting to brown.
Add salmon pieces back into the pan, and stir gently.
Whisk the sauce again to make sure the cornstarch is well incorporated.
Make a well in the center of the pan, then pour in the sauce.
Stir while sauce thickens and turns into a glaze, about 30 seconds, then serve.
Garnish with sliced green onions, if desired.
Notes
This salmon and vegetable stir-fry will last for a day in the refrigerator, but is really best eaten the day you make it.Expert Tips: The trickiest part of this stir fry salmon recipe is making sure that the salmon and vegetables are not undercooked and not overcooked. That is the reason for making the stir-fried salmon first, then removing it from the pan. And that is also the reason for starting by cooking the mushrooms, then broccoli, before adding the rest of the vegetables. If you try to save a step and sauté them all at once, you’ll either undercook the mushrooms or broccoli, or overcook the peppers. Also note that the size of your vegetables will also impact their cook time—I like my broccoli florets fairly small, so that they cook more quickly. Big pieces will take forever to cook.Take care to not stir the salmon around too much, either while you are browning it the first time or when you are stirring it back into the veggie stir fry. Salmon breaks apart super easily, so if you like those big chunks of salmon, handle it carefully!