Preheat the oven to 350°F (177°C) and grease a 9×13-inch pan or line with aluminum foil or parchment paper, leaving an overhang on the sides to lift the finished brownies out (makes cutting easier!). Set aside.

In a microwave-safe bowl, combine the butter and half (2 ounces/57g) of the chopped chocolate. Melt in 30-second increments, whisking after each, until completely smooth. Whisk in the sugar until completely combined, then whisk in the eggs and vanilla. The batter will be light brown and look a bit dull.

Add the cocoa powder, flour, salt, remaining 2 ounces/57g chopped chocolate, and the chocolate chips. Fold it all together with a silicone spatula or wooden spoon. Batter will be very thick. Spread evenly into prepared pan.

Bake for 30 minutes, then test the brownies with a toothpick. Insert it into the center of the pan. If it comes out with wet batter, the brownies are not done. If there are only a few moist crumbs, the brownies are done. Keep checking every 2 minutes until you have moist crumbs. Brownies typically take 31–32 minutes in my oven.

Remove from the oven and place on a wire rack to cool completely in the pan before cutting into squares.

Cover and store leftover brownies at room temperature for up to 1 week.