In a large bowl mix the sugar, cocoa, eggs, vanilla and butter to a smooth paste. Add the chocolate chips and stir through.
Add the sifted flour and baking powder and stir through to combine it.
Pour mixture into a greased and lined tin (30x20cm), bake in a pre heated oven at 150°C (fanforced oven) or 170°C (normal oven) for 25-30 min or until mix is set.
A knife/skewer will come out with melted choc on it but not mixture. Leave in tray until almost completely cool then turn out and cut when cold.
Makes a really yummy dessert when served warm with vanilla ice-cream and berry coulis or chocolate sauce and whipped cream.