Pulse the dressing ingredients in a food processor until smooth. Place the steak strips in a bag and cover with just enough of the dressing/marinade to coat. Set remaining dressing in the fridge for later. Marinade for 30 minutes to 1 hour (but definitely not longer than 1 hour).
Optional (but highly recommended): toast sesame seeds in a dry pan until fragrant. Transfer to a small bowl.
Heat skillet/pan with cooking oil over medium heat. Saute onion for 3 minutes. Then add carrot and bell pepper and cook for 5 minutes. Stir regularly.
Add kale and cook for 2 minutes more or until wilted. Transfer to a bowl or plate.
In same pan, add a little bit more oil and increase heat to high. Pull the steak out of the marinade and discard remaining sauce.
Add the steak to the pan depending on what type of pan you are using. It should sizzle! Let the steak sit for 1-2 minutes to get a golden brown sear, flip if necessary, or just remove from the pan and let it finish cooking on a plate. How long you cook the meat dependents on how well-done you want your steak, but just keep it mind that it cooks quickly because it's sliced very thinly.
When ready, add veggie mix and sauce to the meat. Cook while stirring until heated through.
Top with sesame seeds before serving.