-Preheat oven to 350 degrees F.
-Butter sides and bottom of a 9X13 baking pan.
-Line with parchment paper.
-In a bowl, whisk together flour, salt and cocoa.
-Put the chocolate and butter in a large bowl and set it over a
saucepan of simmering water, stirring occasionally, until chocolate
and butter are melted and smooth.
-Turn off heat, keeping bowl over the water, and add the sugars, then
remove bowl from pan. Mixture should be room temperature.
-Add 3 of the eggs to the chocolate mixture and whisk until
combined. Add vanilla and stir until combined. Do not over mix or
brownies will be cakey.
-Sprinkle flour mixture over the chocolate mixture. Using a rubber
spatula (not a whisk) told flour mixture into the chocolate mixture
until just a bit of the flour is visible.
-Pour into prepare pan and smooth the top. Bake for 30 minutes
rotating pan halfway through cooking time.