Preheat oven to 180°C no fan (see tip). Grease and line base and sides of a 20cm x 30cm lamington pan.
Combine butter, oil and chocolate in a saucepan over low heat. Stir with a metal spoon until melted and smooth. Transfer to a mixing bowl, whisk in the cocoa while the mixture is warm. Set aside to cool 5 minutes. Stir in the sugar then eggs, one at a time, mixing well between each addition.
Stir in the buttermilk. Sift the flour and baking powder together over the mix then gently fold to combine. Pour the brownie mix into prepared pan. Top with raspberries, gently pressing them into brownie mix. Bake 45-50 minutes or until a skewer inserted into the centre has moist crumbs clinging.
Allow to cool in the pan completely before cutting onto pieces. Serve with extra raspberries and cream.