Bottom Chocolate Layer

1. Prepare the Oven and Pan:
   Preheat your oven to 350°F (175°C). Grease a 9-inch square baking pan or line it with parchment paper for easy removal.
2. Mix the Wet Ingredients:
   In a medium mixing bowl, beat the eggs until frothy. Add the melted butter, sugar, and peppermint extract, and mix until smooth.
3. Incorporate the Chocolate:
   Stir in the melted unsweetened chocolate until fully combined. If you prefer a firmer brownie texture, fold in the flour at this stage.
4. Bake the Chocolate Layer:
   Pour the batter into the prepared pan and spread it evenly. Bake for 25 minutes, checking after 15 minutes if making the flourless version. The layer should be set but not overbaked. Let it cool completely for at least 30 minutes.

Middle Mint Frosting

1. Blend the Ingredients:
   In a small bowl, cream the softened butter, cream, peppermint extract, and powdered sugar until smooth. Add a few drops of green food coloring if desired for a festive look.
2. Frost the Bottom Layer:
   Spread the mint frosting evenly over the cooled chocolate layer. Place the pan in the refrigerator for about 5 minutes to firm up the frosting.

Top Chocolate Layer

1. Prepare the Chocolate Topping:
   In a microwave or over a double boiler, melt the chocolate and butter together, stirring until smooth and glossy.
2. Top the Mint Frosting:
   Once the frosting is firm, spread the chocolate mixture evenly over the top. Refrigerate again for about 5 minutes until the topping is set.
3. Cut and Store:
   Remove the bars from the pan and cut into squares or strips. Store in an airtight container in the refrigerator for up to a week.