Preheat the oven to 160Fan/180°C and line a baking tray with parchment paper (approx. 20cm square).
Place a heatproof bowl over a pan of simmering water and break up 150g of chocolate and place in the bowl. Allow to melt and set aside.
Meanwhile, sieve the flour and cacao/cocoa powder into a large bowl. Stir in the sugar and a pinch of salt.
Pour the oil, vanilla and milk along with the melted chocolate to the flour and stir until combined.
Chop the remaining 50g of chocolate and stir most of it into the brownie batter with the berries.
Pour into the lined dish, smooth over the top and sprinkle over the extra chopped chocolate. Bake for 25-30 minutes until springy to touch around the outside.
Cool for 15 minutes in the tin and then cool fully on a wire rack. They will be very soft until fully cooled. Cut into squares.