Preheat oven to broil setting.
In medium size bowl, use a whisk to blend the eggs, Gruyere, pepper, and salt together. You want the egg mixture nice and frothy.
Heat 12-inch non-stick, oven safe sauté pan over medium high heat.
Add butter to pan and melt.
Add sausage to the pan and use a wooden spoon to break up sausage. When the sausage is nice and golden brown remove with a slotted spoon, put it in a bowl and set aside.
Add spinach to pan and sauté until wilted, about 5 – 7 minutes.
When the spinach is wilted add the mushrooms and continue to sauté until the mushrooms soften, about 5 minutes.
Add the cooked sausage back to the pan and pour egg mixture over vegetables. Cook for about 4 to 5 minutes or until the egg mixture has set on the bottom and begins to set up on top.
Place pan into oven and broil for 3 to 4 minutes, until lightly browned and fluffy. Watch carefully!
Remove from pan and cut into 6 servings.
Serve immediately.