Preheat the oven to 350° F (175° C) First, prepare the vinaigrette and set aside.
Slice the mushrooms anyway you like, small or big whatever your preference.
Sauté the mushrooms on medium high with most of the butter until golden Lower the.heat Save some of the butter for greasing the baking dish.
Chop the scallions and mix with the fried mushrooms Add salt and pepper to taste, and mix in the parsley.
Mix eggs, mayonnaise and cheese in a separate bowl Salt and pepper to taste.
Add the mushrooms and scallions and pour everything into a well greased baking dish Bake for 30-40 minutes or until the frittata turns golden and the eggs are cooked.
Let cool for 5 minutes and serve with leafy greens and the vinaigrette.