Coat a skillet with cooking spray and heat over medium-high heat. When pan is nice and hot, add mushrooms, sprinkle with a little bit of salt and pepper and cook for about 2-3 minutes, then turn each piece to cook the other side until nice and golden brown. Transfer to a bowl and set aside.
Put the skillet back over medium heat and when hot enough, add chicken, sprinkle with salt and pepper and cook for about 5 minutes, then flip the pieces and and cook until nice and golden. Add onion and garlic, stir and cook for another 2-3 minutes.
Throw in the zucchini, stir and continue cooking for a minute or two.
Meanwhile, add ingredients for the sauce to a medium mixing bowl and whisk until well combined.
When zucchinis start to become tender, go ahead and add the mushrooms, green onions, cashews and sauce then give that a good stir and simmer for a couple of minutes.
Divide between 2 serving bowl and garnish with green onions, if desired.