Melt the butter in a small saucepan over medium-low heat, stirring and scraping the pan every 10-15 seconds. The butter will melt, foam, then turn golden brown with nutty aroma and small brown bits (about 5-7 minutes). Remove from heat and add cocoa powder and milk or dark chocolate bar in hot butter.Mix thoroughly till there're no lumps in it and set it aside to cool.

Preheat the oven at 166C if you're using dark colour aluminum pan or at 176C if using lighter colour aluminum pan.

Line a square 8 inch baking tin with parchment paper, leaving overhang for easy removal. Lightly grease the paper.

In a bowl add eggs, white sugar, light brown sugar, whisk together until most or all of the sugar granules have dissolved.

Once the sugar has dissolved, add the brown butter, cocoa powder, melted dark or milk chocolate mixture and vanilla extract. Mix everything together.

Add the all-purpose flour and salt and mix just until combined, avoid overmixing.

Fold in the chocolate chips or chunks until evenly distributed.

Pour the batter into the prepared pan and bake for about 30-40 minutes.

Begin checking at the 25 minute mark by inserting a knife into the center. The brownies are done when the edges are set and the knife comes out with a little batter still clinging to it. Depending on your oven, total bake time may be up to 40 minutes.

Let them cool down when they're done baking and then cut them into small bite size pieces.