Saute the onions and mushrooms: Heat oil in a large skillet over medium heat. Add chopped onions and sliced mushrooms and sauce until they start to soften, about 4 minutes. Add the garlic and ginger to the skillet and sauté until fragrant, about 2 minutes.
Cook the ground meat: Add the ground meat to the pan and cook until browned, breaking it up as it cooks. While the meat is cooking, wash and dry your lettuce, cover and place in the fridge until ready to serve.
Add the sauce: Add the Korean BBQ sauce, coconut aminos, brown sugar, and sriracha sauce to the pan and stir to combine.
Add coleslaw mix: Toss in the coleslaw mix and remove from the heat. It will soften slightly from the heat of the filling. You want the mix to be a little crunchy.
Assemble and Serve: Just before serving, drizzle in 1-2 teaspoons of toasted sesame seed oil and mix to combine. Spoon the mixture into lettuce and drizzle with a bit more sriracha, garnish with the green onions and any other desired toppings and enjoy!