Preheat oven to 350° Fahrenheit. Line a 9x13 inch pan with parchment paper. Set aside. Combine the all- purpose flour, cocoa powder, baking soda, and salt and stir with a fork until combined. In the bowl of an electric mixer fitted with a paddle attachment, combine melted butter and sugars. Mix over medium/high speed until the butter is completely combined with the sugar. Add eggs one at time, mixing well after each addition. Stop and scrape the mixer as needed. Reduce the mixer speed to low and add in the vanilla extract. Add the flour mixture and mix just until the flour is moistened. You should still see bits of dry flour. Fold in the chocolate chips, making sure to incorporate the batter almost completely. Do not over-mix. Spread mixture into prepared pan. Use an offset spatula to distribute evenly in the pan. Bake for 20-25 minutes until the top has puffed up a bit, is a light golden brown, and has lost a bit of shine. The mixture should remain under-baked with a bit of a jiggle when you move the pan around. Allow to cool completely and then cut into bars.