Place a rack in the center of the oven and preheat to 350 degrees. Spray an 8" x 8" cake pan with cooking spray or line the bottom with parchment paper and set aside.
Add melted butter to a large mixing bowl and allow it to cool slightly. Stir in sugar, beaten eggs, vanilla and salt until completely combined.
Sift flour, cocoa powder and baking powder over the egg mixture then stir just enough to combine. Transfer the batter into the prepared pan and bake 25–30 minutes until firm in the center.
Remove from oven and set to cool completely on a wire rack before adding the topping. When the brownies are completely cool, it is time to prepare the topping.
Add white chocolate chips and heavy cream to a microwave-safe bowl and heat for 30 seconds. Remove from the microwave and give it a stir. Return to the microwave and heat in 10-second intervals, stirring after each time. Repeat until melted and smooth, but be sure not to overheat the chocolate.
Stir in peppermint extract and just a drop or two of green food coloring if desired. Pour chocolate topping over cooled brownies and spread evenly. Sprinkle top with mini chocolate chips and refrigerate until set. Cut into squares and serve.
One Last Thing
Green food coloring isn’t required, but it’s a lot of fun! It sticks to the St. Paddy’s Day theme and also gives people a heads-up that they’re about to bite into some mint—no surprises!