Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan.

In a medium saucepan over medium heat, melt the butter. Stir in the granulated sugar until smooth, about 3-5 minutes.

Remove the pan from the heat and whisk in the eggs and vanilla extract until fully incorporated.

Gently stir in the flour, cocoa powder, and salt. Mix until just blended; don’t overmix.

Fold in the mint chocolate chips, ensuring they’re evenly distributed throughout the batter.

Pour the mixture into the prepared pan, spreading it evenly.

Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean but moist.

Allow the brownies to cool in the pan for about 30 minutes.

For the mint filling, beat together the powdered sugar, milk, and mint extract in a medium bowl until smooth and spreadable.

Spread the mint filling over the cooled brownies in an even layer.

For the ganache, heat the heavy cream in a small saucepan until it just begins to boil. Remove from the heat and pour it over the chopped semisweet chocolate in a bowl.

Let it sit for 1 minute, then stir until the mixture is smooth and glossy.

Pour the ganache over the mint filling, spreading it into an even layer.

Allow the brownies to set at room temperature for about 1 hour before cutting them into squares.