Preheat the oven to 350 degrees. Grease an 8 or 9 inch square baking pan with butter or non-stick spray and line with parchment paper for easy removal.

In a medium sized saucepan, melt the butter over medium heat. Remove from heat, then whisk in the sugar until smooth and creamy.

Once that is combined, mix in your cocoa and continue whisking until fully combined.

Add eggs one at a time, whisking well after each addition. Stir in the vanilla and salt.

Once all that is mixed very, very well, add in your flour and stir to just to combine, without over-mixing.

Add chocolate chip/chunks and stir, so chocolate starts to melt in.

Pour into prepared pan and swirl mixture with knife to further distribute chocolate and spread evenly. Add more chocolate chips/chunks on top if desired.