Preheat the oven to 350℉. Line or spray an 8x8 baking pan and set aside.
In a small, microwave safe bowl, add your butter and 170g of semi sweet or dark chocolate. Heat in 30 second increments until fully melted.
While the butter mixture heats, add your eggs and sugar to the bowl of a stand mixer or a large mixing bowl. Whisk at medium high speed for 3 minutes until ribbony and lighter in colour.
Once the butter mixture is completely melted, stir in your vanilla. While mixing at a low speed, pour the butter mixture into the egg mixture and mix until combined.
Add the flour, cocoa powder and salt to the egg mixture. Fold together until almost combined.
Add in the chocolate chips and fold until combined. Pour into your prepared pan and smooth it with a spatula. Drop tsp or slightly larger size bits of cookie butter onto the top of the batter. Make sure you drop them all over the top of the batter so every bite gets some cookie butter. You can push them down and swirl them a little here if you like.
Place in the oven and bake for 25-29 minutes or until a toothpick comes out almost clean. If it comes out clean then the brownies are overbaked so err on the side of caution and pull them earlier rather then later.
Allow to cool completely before storing in an airtight container for up to 3 days. Enjoy!