Preheat the oven to 180C/350F. Line an 8 x 8-inch pan with parchment paper and set aside.
In a large mixing bowl, add your flour, cocoa powder, and superfine sugar and mix together. In a microwave-safe bowl, add one cup of the chocolate and microwave in 20-second spurts until melted. Add the condensed milk, oil, and milk and whisk together until smooth. Combine your wet ingredients into the dry ingredients and mix until just combined. Fold through the remaining chocolate.
Transfer the brownie batter into the lined pan and bake for 30-35 minutes, or until a skewer comes out clean.
Remove the brownies from the oven and let them cool completely, before slicing and serving.
TO STORE: Leftover brownies can keep at room temperature, covered, for up to 1 week. If you'd prefer thicker and cakier brownies, refrigerate them and they will keep for up to 2 weeks. TO FREEZE: Place brownies in a ziplock bag and store them in the freezer for up to 6 months.