Combine the flour, sugar and cocoa powder in a large bowl.
Add the oil, vanilla extract, milk and melted chocolate. Use the whisk to combine the wet and dry ingredients initially, then swap the whisk for a wooden spoon and stir until the mixture is fully combined. This is to ensure that you remove any initial clumps of flour but don’t overwork the batter.
Stir in the chocolate chips until just combined.
Pour the brownie mixture onto the prepared tray. Use the back of a wooden spoon to level out the mixture.
Bake for 20-24 minutes.
Allow the brownies to cool on a wire rack for about 15 minutes. Cut into squares and serve – or follow our freezer method above for extra fudgey brownies!