Preheat the oven to 350 and grease a 9x13 baking dish.
In a small sauce pot, over medium heat, start melting butter and add chocolate chips, vanilla extract and sugar. Keep stirring with a silicone covered whisk until all melted and smooth.
Transfer the mixture into a large mixing bowl.
Whisk in buttermilk until combined.
Whisk in eggs until combined and smooth.
Whisk in flour, cocoa powder, baking powder, baking soda and salt. Whisk until all smooth and all incorporated.
Fold in chocolate chips and transfer into the baking dish.