Add the eggs to a large mixing bowl and whip with a whisk until the yolks break. Add melted butter, brown sugar, white sugar, vanilla and optional peppermint extract to the bowl and mix well.
In a second bowl, mix together the flour, cocoa and salt until combined. Add this mixture to your wet ingredients and mix until just combined with a silicone spatula to make the brownie batter.
Pour the batter into the pan. Use your spatula to spread the batter evenly in the pan.
Bake brownies for about 25-28 minutes or until when you insert a toothpick in the center, the brownies are fudgy but not wet with batter. Allow the brownies to cool but leave them on the foil.