1Preheat oven to 350 F (180 C or Gas Mark 4)
Line an 8-inch square cake pan with parchment or wax paper and then butter the paper.
2In a bowl, cream butter and brown sugar, then beat in the eggs, one at a time. Sift the cocoa and flour together into the bowl, then add the coconut and stir until well combined. Spread mixture firmly and evenly into prepared pan and bake for about 35-40 minutes. It will still be soft while hot but will firm up as it cools. Allow to cool in pan. When completely cool, turn onto a wire rack for frosting.
3For the frosting, cream the butter and cocoa, then stir in the sifted confectioners' sugar. Gradually stir in enough milk to make a thick frosting. Spread evenly over brownies and cut into squares.