Preheat oven 350
Spray a 8x8 inch pan with non-stick spray, line with parchment and set aside
In a small bowl, whisk together the flour, baking soda and salt then set aside
In a medium microwave safe mixing bowl, add the butter and sugar and heat on high for about a minute until butter is melted then whisk until smooth
Whisk in the cocoa powder and vanilla
Whisk in the egg and the egg yolk until well combined
Whisk in the flour mixture until just combined
Stir in your chocolate chips and/or chunks using a spatula to make sure you have all the dry ingredients well incorporated, then scrape the brownie batter in to the middle of the prepared pan and spread gently to the edges.
Dot with a few more chocolate chunks if desired!
Bake 35-38 minutes or until a toothpick placed in the center just has wet crumbs.
Remove from the oven and let cool completely before removing from the pan, slicing and serving!