If portobello mushrooms are already sliced, slice them thinner.
Heat oil in a sauté pan. Add mushrooms. Sauté for 5 minutes. Add teriyaki sauce. Add more sauce if the mushrooms are not all coated; you want them to be generously covered in sauce. Cook, stirring occasionally, until mushrooms are cooked well. Set aside.
Combine all dressing ingredients.
Toss mushrooms with greens, spiralized vegetables and dressing.