Preheat oven to 350°F. Line a 9-inch baking dish with parchment paper. Set aside.
In a medium sized saucepan, melt butter over medium heat. Remove from heat and add in chocolate chips and sugar.
Stir until chocolate is completely melted. Add in eggs, one at a time, stirring completely after each addition. Stir in vanilla.
Add the cocoa powder, flour, salt, and baking powder. Using big strokes, stir in JUST until mixed and no longer see dry ingredients. DO NOT BEAT OR OVER STIR.
Pour batter into dish and bake for about 35 minutes. Remove from oven and cool completely before adding filling.
For the filling, beat softened butter with powdered sugar, peppermint extract, food coloring, and milk. Beat for about 3-4 minutes, until fully combined and fluffy.
Spread over cooled brownies. Refrigerate while you make the ganache.
For the ganache, heat cream in small saucepan until warm (not boiling). Remove from heat and whisk in the chocolate chips until smooth.
Pour immediately over green layer on the brownies and spread evenly with an offset spatula. Return to refrigerator for one hour.
Slice and enjoy.
Notes
Line your baking dish with parchment paper before adding the brownie batter. Easy removal and easy clean up!
Do not let the cream simmer or boil when making the ganache. Boiling or scalding the cream will ruin the consistency.
Be careful not to over stir the brownie batter. Use big strokes to mix in the dry ingredients just until you no longer see big lumps of flour. Over mixing will make your brownies tough.