Fill the bottom of a large skillet with about a 1/2-inch of water and bring to a low boil. Turn off heat, add the block of tempeh, cover and allow to steam for 10 minutes.
Meanwhile, prepare the marinade. In a large bowl whisk together the tamari, rice wine vinegar, sriracha, coconut sugar, garlic powder and ginger. Set aside.
Once the tempeh is done steaming, transfer to a cutting board to cool. Using your fingers, crumble the tempeh into the bowl with the marinade. Stir until the tempeh absorbs all of the marinade.
In the large skillet, warm 2 tablespoons sesame oil over medium heat. Add the finely chopped onion and cook for about 3 minutes, until translucent. Add the tempeh to the skillet and stir to combine. Cook for another 2 minutes.
To the skillet, add the entire package of slaw. Stir as it cooks, for about 5 minutes. You can cook it shorter or longer depending on how crisp or soft you prefer the vegetables.
Serve warm topped with green onion and sesame seeds, and enjoy!
If using toasted sesame oil you may want to reduce amount since the flavor is much stronger. You can also substitute olive oil or whatever neutral flavored oil you have on hand.