Preheat broiler to high and adjust the rack so it is about 6 inches from the heat.
In a small bowl beat the eggs well until frothy. Season with 1/8 tsp pepper and 1/16 tsp salt.
Heat oil in a cast-iron skillet over medium-high heat. Saute the mushrooms until browned. About 4-5 minutes. Stir in spinach and remaining salt and pepper. Cook for about 1 minute or until the spinach is wilted.
Add eggs and stir slowly. After 2-3 minutes sprinkle the top with cheese.
Place the pan under the broiler for abut 2 minutes. Then transfer to a plate and serve.