For the brownies: Add flour, whey protein, cocoa powder, salt, and Stevia in a large mixing bowl. Whisk thoroughly until no clumps remain.
Combine Greek yogurt, egg whites, and vanilla extract with the dry ingredients. Whisk until a thick brownie batter forms.
Adjust the oven rack to the middle position and preheat oven to 350°F (177°C). Transfer brownie batter to a 9x9 baking dish with parchment paper and bake for 16 minutes.
Allow brownies to cool for 30 minutes before adding frosting.
For the mint frosting layer: Place cream cheese in a microwave safe dish. Heat for 20-30 second intervals in the microwave and stir until fully softened.
Combine softened cream cheese with the Greek yogurt, mint extract, maple syrup, and green food coloring. Whisk ingredients to make the frosting.
For the chocolate layer: Place chocolate chips in a microwave safe bowl. Heat for 20-30 second intervals in the microwave and stir periodically.
Spread melted chocolate on top of mint frosting layer. Allow the chocolate to harden in the refrigerator for 1 hour before eating.