Preheat the oven to 350°F (175°C) and line a 9-inch square baking pan with foil, greasing it lightly.
Melt the butter and chocolate chips together in a microwave-safe bowl, stirring until smooth.
Mix in sugar, then add eggs one at a time, whisking after each. Stir in vanilla extract.
Combine dry ingredients (flour, baking powder, salt) in a separate bowl, then slowly mix them into the wet ingredients.
Add green food coloring and mix until the batter is evenly colored.
Pour the batter into the pan and bake for 44-48 minutes, until a toothpick inserted comes out with a few moist crumbs.
Let the brownies cool completely in the pan before frosting.
Make the frosting by beating together cream cheese, butter, powdered sugar, salt, and vanilla extract until smooth.
Spread frosting evenly over the brownies, slice into squares, and serve!