Preheat oven to 350 degrees and spray a 9×13 baking pan with baking spray.
Whisk together cocoa powder and melted butter until smooth.
Whisk in sugar, brown sugar, eggs, and vanilla.
Set the oven to 350ºf and spray a 9×13 baking pan with baking spray.
In a mixing bowl, add the cocoa powder to the melted butter and mix until smooth.
Mix in the sugars, eggs, and vanilla.
In a separate bowl mix together the flour, cornstarch and salt then gradually mix it into the wet ingredients until just smooth.
Pour the batter into the baking pan, spread it around the whole pan and bake for 18 minutes.
Cool completely.
Add chocolate chips and heavy cream to a large microwave safe dish and melt for 60 seconds, let rest for a couple of minutes and then stir until smooth.
Smooth the ganache over brownies and sprinkle candy chocolate chips while ganache is still wet.