Preheat the oven to 350 degrees F. Spray the cups of a mini muffin tin with non-stick cooking spray and set aside.
Place chocolate and butter in a large microwave-safe mixing bowl. Microwave in 30-second intervals, stirring in between each heating, until the chocolate and butter are melted and smooth.
Stir in the granulated sugar and brown sugar. Then, mix in eggs and vanilla extract.
Sift in the cocoa powder, salt, and flour and stir until the brownie batter is well combined.
Scoop 1 tablespoon of batter into each mini muffin tin cup.
Bake for 10-15 minutes, or until a toothpick inserted comes out almost clean but not wet.
Remove the brownies from the oven and allow them to cool in the muffin tin. Then, run a sharp knife around the edge of the brownies and pop them out.
Notes
Recipe yield may vary slightly depending on how much batter you put into each muffin tin cup and the size of your muffin tin.