In a medium bowl, whisk together the flour, cocoa powder, and salt. Set aside.
In a medium saucepan over medium-low heat, melt the butter to just simmering. Turn off the heat and add the chopped chocolate. Swirl the pan so the chocolate is submerged in the butter and let sit for 3 minutes. Gently whisk until smooth.
In a stand mixer fitted with the whisk attachment, whip together the eggs, sugar, and vanilla on medium-high speed until light and fluffy, about 5 minutes. Turn the speed to low and slowly add the melted chocolate mixture.
Add the flour mixture to the chocolate mixture and mix just until combined. Allow to cool to room temperature; you can speed this up by putting it in the refrigerator. As it cools, the mixture will become thick enough to scoop.
Stir the cookie batter before scooping. Using a 1-ounce scoop, portion out the cookie dough. Freeze the cookies for at least 15 minutes. The cookies can be made several days in advance and stored tightly covered in the freezer.
Preheat the oven to 375°F. Line baking sheets with parchment paper or a silicone mat.
Position the frozen cookies 2 inches apart on the prepared baking sheets. Bake until set around the edges, about 12 minutes. The cookies will puff up and then will collapse slightly as they cool.
Allow the cookies to cool slightly on the baking sheet before removing to a wire rack.