Preheat the oven to 350°.  Butter or spray the bottom and sides of a 9 x 13-inch glass or light-colored metal baking pan.

In a medium mixing bowl, whisk the flour, salt and cocoa powder together.

Place the chocolate, butter and espresso powder in a large glass bowl, set over a saucepan of gently boiling water; ensure the bottom of the glass bowl does not touch the water.  Stir the mixture occasionally until the chocolate and butter are melted and the mixture is smooth.  Turn off the heat, leave the bowl on the saucepan, and add the sugars, whisking until combined.  Remove the bowl from the pan.  Add 3 eggs to the chocolate mixture, whisking to combine.  Add the remaining 2 eggs and vanilla to the mixture and whisk again to combine.  Do not overmix the batter at this point or your brownies will not be soft and fudgy.

Add the flour mixture to the chocolate mixture and use a spatula to fold the flour into the chocolate until mostly mixed, but with a little flour still visible.  This will ensure you don’t overmix the batter.

Pour the batter into the prepared baking pan and spread to the sides.  Bake in the center of the oven for 30 minutes, rotating the pan halfway through the baking time.  When a toothpick inserted into the center of the brownies comes out with a few moist crumbs sticking to it, remove the brownies from the oven.  Cut the brownies into squares to serve, either while warm (yes!) or after completely cooled.