Combine baby spinach, almond milk, yogurt, egg whites, and vanilla in a blender, place on lid, and blend until liquified and well combined.
Add in oat flour, sweetener, cinnamon, salt, and baking powder. Blend again until everything is combined. The batter may will look fairly thin but will thicken as is sits.
Stir in rolled oats and chopped walnuts (or preferred stir-in). Let the batter rest for 10 minutes before making your pancakes as this will allow the rolled oats to soften and the batter to thicken.
Heat a large non-stick saute pan over medium-low heat and coat it with a thin layer of non-aerosol cooking spray, butter, or coconut oil. Once the skillet is hot, drop a scant 1/4 cupful of batter into the pan (I like to keep the pancakes on the smaller side).
Cook gently for 3 to 4 minutes on the first side, until the pancakes look dry around the edges and small bubbles form over the top.
Flip, and cook on the other side for another 1 to 2 minutes. They will be golden on both sides and set through the center. Repeat with the remaining batter.