Heat oven to 180C (160 fan-forced). Grease and paper line a slice tin. Combine butter, sugar, eggs and vanilla essence in a bowl.
Sift together flour, cocoa, baking powder and salt. Add 3/4 cup of coconut and optional pistachio nuts. Add to butter mixture. Mix together well.
Spread mixture evenly over base of tin. Sprinkle remaining 1/4 cup of coconut over top.
Bake 25 - 30 minutes or until brownies begin to pull away from sides of tin. Cool completely in tin. Cut into squares.