Preheat your oven to 350°F and lightly grease two 4-inch mini cake pans with a touch of coconut oil.
In a medium mixing bowl, whisk the liquid egg whites until they become light and frothy.
Stir in 0.25 cup of the Greek yogurt, the melted coconut oil, and the vanilla bean paste until well combined.
Add the oat flour, vanilla protein powder, baking powder, monk fruit sweetener, and sea salt to the wet ingredients, folding gently until a smooth batter forms.
Divide the batter evenly between the two prepared cake pans.
Bake for 18 to 22 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean.
Remove the cakes from the oven and allow them to cool completely on a wire rack before removing from the pans.
In a small bowl, mix the remaining 0.25 cup of Greek yogurt with an optional drop of monk fruit to create a thick frosting.
Place one cake layer on a plate, spread half the frosting on top, place the second layer over it, and finish with the remaining frosting.