In a medium bowl, whisk together the eggs, cocoa powder, salt, baking powder, and vanilla. Set aside.

In a medium microwave-safe bowl, combine the butter and sugar. Heat in the microwave for 30 seconds at a time until the butter is melted.

Add the hot butter mixture to the cocoa mixture. Whisk until smooth. Stir in the flour, and then stir in 1/2 cup of chocolate chips until melted. Let cool for 15 minutes.

Meanwhile, preheat your oven to 350F. Butter and line an 8×8″ baking pan with parchment paper.

Once the batter has cooled, stir in the rest of the chocolate chips and spoon the batter into the prepared baking pan. Spread the batter out evenly in the pan.

Bake for about 25 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. The edges should be set, but the center should still look moist. Let cool before cutting into squares.