Preheat the oven for 10 minutes. Grease the tin with butter and place a parchment paper over it. Take butter and chocolate chips in a bowl and melt it over a double boiler. Then keep it aside. In a bowl take powdered sugar dissolve it in water and then add vanilla essence to it. Add melted chocolate to it. Whisk until all the ingredients are mixed properly. Then shift the dry ingredients (all-purpose flour, baking soda, baking powder). Mix well.

Pour the batter into prepared pan. Even it properly. Bake it in a pre-heated oven for 30 minutes. Pierce a tooth pick to check if the brownie is baked properly or not.

Assembling:
Let the brownie cool properly. Before cutting it into pieces keep it in refrigerator for one hour. Then remove the brownie from the pan with the help of parchment paper. Cut it into desired shape and size.