Preheat oven to 350°F (175°C) and prepare an 8x8 inch baking pan with non-stick cooking spray.

In a medium-sized bowl, whisk together the protein powder, cocoa powder, coconut flour, baking powder, and erythritol.

In a separate large bowl, whisk the egg whites, 150g of Greek yogurt, and almond milk until the texture is uniform.

Slowly add the dry ingredient mixture into the wet ingredients, stirring constantly until a thick batter forms.

Gently fold in half of the crushed Oreo cookies into the batter.

Spread the batter evenly into the prepared baking pan and smooth the surface with a spatula.

Bake for 22 to 25 minutes, or until a toothpick inserted into the center comes out clean.

Remove from the oven and allow the cake to cool completely to room temperature before frosting.

Prepare the frosting by mixing the remaining 100g of Greek yogurt with 15g of vanilla protein powder until smooth and creamy.

Apply the frosting to the cooled cake and top with the remaining crushed Oreo cookies.