Mix together the oil, Dijon, vinegar, lemon and spices
Stir in mushrooms and get well coated (you could add green onion as well)
Set aside to combine and rest for at least an hour at room temp (I cover with plastic wrap for safety) (I've also done this ahead of time and stored in fridge till needed up to 3 days later)
Mix in walnuts, blue cheese, lettuce and tomatoes ----- you can also serve this deconstructed where each item sits atop the lettuce bed