Preheat your oven to 375 degrees Fahrenheit. This ensures a consistent baking environment for your quiche.
Take the rolled oats and place them into a food processor or blender. Pulse until you achieve a coarse flour texture. This will be the base for your oat flour.
In a large mixing bowl, combine the oat flour with whole wheat pastry flour and salt. This mixture will create the crust. Make sure it's well combined.
Now, add the coconut oil into the flour mixture. Incorporate it in small pieces, either using a pastry cutter or your hands. Blend until the mixture resembles pea-sized crumbles.
Slowly add ice cold water in small amounts. This will help the dough come together. The texture should be shaggy and dry but cohesive when pinched.
Form the dough into a ball and wrap it tightly in plastic wrap. Refrigerate for 30 minutes to 24 hours. This step helps the dough firm up.
Once chilled, roll the dough out on a floured surface. Carefully place a quiche or pie pan upside down on the dough to cut out a circle. Gently turn it over and press the dough into the pan, trimming the edges as needed.
Using a fork, crimp the outer edges of the crust or fold them over for a rustic look. Ensure it’s well-formed to hold all the filling.
In a skillet over medium heat, add olive oil and heat up. Sauté onion and garlic for about 5 minutes until the onion is soft and translucent. Add spinach and cook until wilted. Remove from heat and mix in the sun-dried tomatoes.
In a separate bowl, whisk the egg whites until frothy. In another bowl, beat the whole eggs until well combined. Mix the two together and then add parmesan cheese, salt, and black pepper.
Gently fold in the sautéed spinach and tomato mixture into the egg batter. Pour the filling into the prepared crust, spreading it evenly.
Bake in the preheated oven for around 25 minutes or until the center is set and the edges are golden. If you like, sprinkle some walnut pieces on top during the last 5 minutes of baking.
