Combine the ingredients for the marinade into a large measuring bowl. Whisk until well combined then pour half of the marinade into a ziplock bag. Cover and reserve the remaining marinade for later use. Slice the chicken into thin bite-sized strips. Place into the zip lock bag then seal and refrigerate for 2-3 hours. Remove the chicken from the refrigerator 20 minutes prior to cooking.
Heat half of the canola oil in a large sauté pan. Add the onion and cook for 2 minutes. Add the shiitake mushrooms and continue cooking for 1-2 minutes, stirring often. Add the kale and minced garlic then season with sea salt and freshly cracked pepper, to taste; toss to coat evenly then cook, stirring constantly, for 1 minute. Remove from the pan and pour into a bowl.
Add the remaining oil to the pan and heat over medium-high heat until hot. Use a slotted spoon and add half of the chicken to the hot skillet (without the marinade). Cook, stirring occasionally, for 2 minutes. Pour into the bowl with the veggies. Add a bit more olive oil, if the pan needs it, then add the remaining chicken (without the marinade). Cook, stirring occasionally, for 2 minutes. Pour into the bowl with the veggies. Discard the zip lock bag and marinade.
Whisk the reserved marinade from earlier until well combined then add to the skillet over medium heat. Whisk for a few seconds then add the chicken, veggies, and any juices back into the sauté pan. Stir to coat evenly and heat through. Serve over rice immediately and garnish with green onion. Enjoy.