Preheat oven to 180C / 350F and line an 8x8 baking pan with parchment paper.
In a saucepan, add condensed milk and butter over low- medium heat, stirring frequently. Once the butter has melted, remove the mixture from heat.
Add in vanilla extract and brown sugar, stir to combine.
Mix in flour, baking powder, cocoa powder and salt until thoroughly blended.
Now, pour the batter into the baking pan.
Bake for 25-30 minutes or until the middle of the brownie is just set.
Let it cool, then cut and serve.
Notes
It is important not to overmix the mixture after the plain flour and unsweetened cocoa powder have been combined. Overmixing results in a less fudgy brownie.