Crank the oven to 300°F.
Lube an 8-inch square baking pan with nonstick spray. Trim a piece of parchment paper so that it fits just inside the baking dish with overhang on two sides (like a sling) and place it inside the pan.
Beat the eggs in a stand mixer fitted with the paddle attachment at medium speed until fluffy and light yellow, 2 to 3 minutes.
In a separate bowl, sift together the granulated sugar, brown sugar, cocoa powder, flour, and salt. Drop the mixer speed to low and slowly introduce the sugar mixture. Follow with the butter and vanilla. Continue mixing until you’ve got a nice, smooth goo. Do not overmix.
Pour the batter into the prepared pan.
Bake the brownies for 15 minutes, then remove from the oven for 15 minutes.
Put them back in the oven until an instant-read thermometer inserted into the middle of the brownie reads 195°F, about 30 minutes.
Cool in the pan for 30 minutes, then transfer the brownie to a cooling rack using the parchment paper as a sling.
Cool 10 minutes more, then cut the brownies into 16 pieces using a pizza wheel and move to a rack to cool completely before serving.