Preheat the oven to 350°.
Cream together butter and sugar in a stand mixer or electric hand mixer. Add eggs one at a time.
Add vanilla and cocoa. Mix together until combined.
Add flour one cup at a time and mix until combined.
Pour batter in a greased 9x13 pan and bake 30-35 minutes. Allow to cool completely before frosting.
Place butter for frosting in a medium bowl and mix with an electric hand mixer to creamy. Add 2 Tbsp milk, mint extract, and food coloring; mix well.
Mix in powdered sugar 1/2 c. at a time. Add remaining 1/2 Tbsp milk and mix together.
Spread frosting over cooled brownies; cover and place in the fridge for at least one hour.
Place semisweet chocolate chips and 1/4 c. butter in a microwave safe bowl. Heat for 20 seconds, stir, heat for 20 more seconds, then stir again until smooth.
Pour chocolate mixture over chilled brownies. Cover and place in the fridge to the chocolate hardens. Cut with a sharp knife to serve. Enjoy!
