In a medium saucepan, combine butter, cocoa powder, and brown sugar. Cook and whisk over medium heat until the butter has melted. Remove from heat and set aside.

In a large bowl, whisk together eggs, granulated sugar, vanilla, instant coffee (if using), and salt until the sugar has dissolved and the mixture seems light and foamy, about 3 minutes. Whisk in melted butter mixture. Gently fold in all-purpose flour and chocolate chips (reserve a few to sprinkle on top of the brownies).

Bake the brownies until they are set and an interted toothpick comes out with a few moist crumbs attached, about 30 minutes. Cool the brownies completely before slicing.