Set the rack in the middle of the #oven{} and preheat to 350°F.

Line a #13 x 9 x 2-inch pan{} with #parchment paper{} (bring parchment up sides of pan so there is a slight overhang) and grease with butter or nonstick cooking spray.

Place the @unsalted butter{2 sticks} in a #medium microwave-safe bowl{} and melt in the #microwave{} until bubbling.

Add the @semi-sweet chocolate{8 ounces} and whisk until the chocolate is completely melted. The heat from the butter should be enough to melt the chocolate completely, but if not, place the chocolate-butter mixture in the microwave and heat for 20 seconds or so, then whisk again. (Alternatively, combine the butter and chocolate in a heat proof bowl and set over a pan of simmering water. Stir occasionally until melted.)

Whisk the @eggs{4} in a #large bowl{}.

Add the @salt{0.5 tsp}, @granulated sugar{1 cup}, @firmly packed dark brown sugar{1 cup}, and @vanilla{2 tsp}; whisk until smooth (be sure no lumps of brown sugar remain).

Whisk in the chocolate-butter mixture, then add the @all-purpose flour{1 cup} and whisk until the batter is uniform.

Pour the batter into the prepared pan and spread evenly.

Bake for about 45 minutes, until the top has formed a shiny crust and the batter is moderately firm.

Cool completely in the pan on a rack. If not serving right away, store them at room temperature, for 3 to 4 days.

To cut brownies, first lift them out of the pan using the parchment overhang and transfer them to a cutting board. Separate the parchment from the edges. Using a sharp knife, trim away the edges and cut the brownies into 2-in squares.