Preheat oven to 350° F/175° F. Line an 8-inch square baking pan with cooking spray and parchment paper.
In a small bowl melt the butter in the microwave for 30 seconds until melted. Pour melted butter into a large mixing bowl. Whisk in granulated sugar and brown sugar until smooth and shiny.
Use a whisk to combine the eggs and vanilla until they're just barely combined; don't over-mix. Whisk in melted chocolate until combined and smooth.
Use a sieve to sift flour, cocoa powder, and salt into the wet mixture. Use a rubber spatula to stir in the dry ingredients until just combined. Stir in whole chocolate chips.
Pour into prepared pan and smooth it out. Bake in the preheated oven for 25-28 minutes, or until the edges are firm and and the top is shiny and slightly cracked. For very gooey brownies, you'll want to pull them out closer to 27 minutes.
Remove brownies from the oven and allow them to cool completely in the pan before slicing.