Preheat the oven to 160°C. Line a 20cm brownie tin or deep roasting pan with baking paper and grease with nonstick spray.
1. Heat the condensed milk and butter in a saucepan until melted, then remove from the heat.
2. Add the sugar and vanilla essence and mix well. Sift the cocoa powder, flour, baking powder and salt together and add to the condensed milk mixture. Mix until a smooth batter forms then spoon into the prepared baking tin or roasting pan. Sprinkle the chocolate over (if using).