Preheat the oven to 350°F/180°c. Line a 9-inch/20cm square baking tin with baking parchment and set aside.
Add the chopped semi-sweet chocolate and cubed butter to a large microwave safe mixing bowl. Microwave in 30 second increments, stirring well in between, until melted.
Add the entire contents of the can of condensed milk, granulated sugar, eggs and vanilla extract to the melted chocolate mixture, and whisk until well combined.
Add the flour, cocoa powder and salt to the mixture and mix until just combined. Fold through the chocolate chips.
Pour the batter into the prepared baking tin and smooth the surface. Bake for 25-30 minutes, or until the edges have set and the center is still soft.
Allow the brownie to cool completely in the tin before removing and slicing.
Notes
Whisk thoroughly after adding the condensed milk mixture for that shiny top.
Do not overmix once the flour is added. Mix just until no streaks remain.
Let the brownies cool fully before slicing for clean edges