Gluten Free Crust (or use your favorite pie crust recipe):
Pre-heat oven to 350° Mix dry ingredients in a large bowl or food processor. Knead in butter or oil and egg until it is thoroughly mixed and forms a ball. Let the ball sit for 10 minutes. Grease a pie pan and press dough into the pan with your hands to get an even layer all over the pie pan, evenly covering the entire pie pan. Pre-cook crust in the oven for 10 minutes or until golden.
Cook your veggies: In a skillet on medium heat olive oil, garlic and onions/shallots until they are translucent. Add in mushrooms and stir for 5 minutes or so until mushrooms begin to soften. Add fresh spinach and stir until wilted. You don’t want to completely cook the mushrooms and spinach, rather just cook out some of the water.
Make custard: In a bowl or food processor the eggs, half and half or other milk alternative, salt and pepper and any other seasoning (rosemary is a great addition!) until thoroughly combined–the longer you mix it the fluffier your quiche will get.
Take the pie crust out of the oven, sprinkle the bottom with half of the cheese. Add the cooked spinach and mushrooms, spreading evenly through the pie crust. Carefully pour the custard filling over the veggies, almost to the brim. Sprinkle the rest of the cheese on top.
Carefully transfer to the middle baking rack and bake on 350° for approximately 50 minutes. Remove when top is golden brown and center is almost-firm. Let cool and set for 15 minutes before serving. Keeps in the fridge for a week and freezes beautifully.