Preheat the oven to 350°F (177°C). Line baking sheets with parchment.
In a medium mixing bowl, sift together flour (1 1/4 cups), cocoa (3 tablespoons, plus 1 teaspoon), baking powder (1/2 teaspoon), and salt (1/2 teaspoon); set aside.
Set a heatproof bowl over a saucepan of very hot, but not boiling water, not allowing the bottom of the bowl to touch the water. Add the chopped chocolate (1 pound, plus 4 ounces), stirring occasionally, until melted. Remove from saucepan and cool for 5-10 minutes.
In a medium mixing bowl, using a handheld electric mixer, cream the butter (1/2 cup, plus 2 tablespoons) and sugar (2 1/4 cups) on medium speed, until light and fluffy. Add the eggs, one at a time, mixing until combined. Increase the speed of the mixer and beat for a couple of minutes until the batter is very light, creamy, and pale in color.
Add the cooled chocolate and the vanilla (1 tablespoon) to the butter mixture, stirring just until combined.
Increase the mixer speed to high and continue to beat until the batter is very light, creamy, and light in color. Stir in the dry ingredients. Stir in chocolate chips (2 cups).
Using a large cookie scoop, portion the dough onto prepared cookie sheets, 2 inches apart. Flatten the dough slightly.
Place cookie sheet in preheated oven and bake for 14-16 minutes, rotating halfway through baking, or until tops are softly set and they're evenly cracked all over.
Let cookies completely cool on the baking sheet. Use a thin metal spatula to remove.