Heat oven to 350 F (180C) and prepare an 8x8 inch pan by lightly greasing it and lining it with parchment paper. This will make for much easier removal and cutting of the brownies.
Place the chocolate chips for the batter, butter, and cocoa powder in a heatproof bowl set over a pan of simmering water. Keep stirring with a spatula until the chocolate and butter melt and texture is smooth and combined. Set aside to cool while you prepare the rest of the ingredients.
In a small bowl, whisk together flour and salt. Set aside.
In the bowl of an electric mixer, add the eggs, brown sugar, and vanilla. Whisk on medium low speeed until combined, 1-2 minutes. Use a spatula to scrape the sides of the bowl if you need to. Increase the mixer to medium and slowly pour in the chocolate mixture. Continue whisking on medium until the batter is smooth, about 1 minute.
Sprinkle the dry ingredients over the batter all at once and use spatula to fold until JUST combined. A few flour streaks are fine. Add the chocolate chips for the mix in, and stir to just combine.
Pour the brownie batter into the prepared pan, smoothing out the top. Bake for 25-30 minutes or until a toothpick inserted in the center comes out with a few moist crumbs attached. It shouldn't be completely dry at all- the brownies will set further out of the oven.
Cool completely in the pan, then lift out brownies with the parchment paper overhang and slice. I got 16 squares!