Preheat oven to 350 degreesHeat coconut oil in a large skillet on medium heat.Saute the mushrooms (and onions and peppers if using) for about 5-6 minutesThen add the spinach and cook for about 4 more minutes or until tender.Drain the excess liquid very well.In a large mixing bowl, whisk the eggs until combined. Add the cooked mushrooms, spinach, onion, red pepper and cheeses (if using) and mix well.Divide the mixture evenly between the muffin tin.Bake at 350 degrees for 20-25 minutes, until set and a knife inserted in the center comes out clean.Store in the refrigerator or freeze. Just pop them in the microwave when you're ready to eat them.