Preheat oven to 450 degrees F (230 degrees C).
Place the 9-inch Pie Crust (1) into a glass or ceramic pie plate. Press bottom and sides into plate, and finish the edges of the crust by pressing the tines of a fork against the rim of the crust. Refrigerate crust until oven is preheated.
Place pie plate into the oven, and bake pie crust 6-7 minutes until set and just starting to brown. Remove crust from oven, and set aside. Reduce oven temperature to 325 degrees F (160 degrees C).
In a large skillet, heat some Olive Oil (1 tablespoon) over medium heat. Add the Yellow Onion (1/2) to the skillet, and sauté 2-3 minutes.
Add Button Mushroom (8 ounce) and a pinch of Kosher Salt. Cook 5-7 minutes, stirring occasionally. After 5-7 minutes, vegetables should be tender, and mushrooms should have given off their liquid. Transfer to a small bowl.
Add more Olive Oil (1 tablespoon) to the skillet, and add the Kale (3 cup). Cook 1 minute, stirring. Add Water (3 tablespoon) and cook until kale is wilted, and water has evaporated, stirring occasionally, 2-3 minutes. Add kale to onion mixture and set aside.
In a medium bowl, add the Egg (4), Milk (1/2 cup), Heavy Cream (1/2 cup), Ground Nutmeg (1/2 teaspoon), Kosher Salt (1/2 teaspoon), and Freshly Ground Black Pepper (1/2 teaspoon). Whisk to combine.
Add the kale mixture and Fontina Cheese (1 cup) and Parmesan Cheese (1/4 cup).
Stir to combine, then pour into pie crust and bake 45 minutes, until filling is set. Remove from oven.
Let quiche cool (around 30 minutes) before serving.