Preheat oven to 325°F
Melt butter in a small saucepan over medium-low heat.
Combine sugar and cocoa powder in a large bowl; stir in melted butter until mixture is smooth.
Stir in 1 egg, vanilla, and salt. Mix in second egg.
Fold in flour and transfer to ungreased 8×8-inch square baking dish.
Bake in the preheated oven for about 35 minutes.
Remove from oven and cool in the baking dish for 10 minutes before removing to cool completely on a wire rack.
Mix powdered sugar, milk, and mint extract in a bowl until smooth.
Pour icing over cooled brownies. Spread evenly and allow to set, about 30 minutes.
Slice into 16 brownies.