1. Preheat oven to 350°F. Prepare a 9×9 inch pan with non-stick spray or parchment paper. Set aside.
2. In a large bowl with a whisk, mix together the melted butter, sugars, vanilla, eggs, and melted chocolate. Once totally combined, add the cocoa powder, instant espresso powder and the kosher salt and whisk until fully incorporated. Add the flour and mix until combined.
3. Using a rubber spatula, pour all of the batter into the prepared pan and bake in the preheated oven for 30-40 minutes, checking after 30 to see if it is done. You will know it is done when the middle is no longer wobbly and a toothpick inserted in the center comes out fairly clean.
4. Allow brownies to cool completely before attempting to frost it.

For the frosting:

1. In a clean, large bowl of a stand mixer with the paddle attachment, or in a clean bowl with a hand mixer, beat the butter and cream cheese together until totally smooth and combined. Be sure the butter is fully combined and that there are no chunks suspended in the mixture.
2. Dissolve the espresso powder in the vanilla extract and add that, 1 cup of powdered sugar, the cocoa powder, and the salt to the creamed butter and cream cheese. Beat together until combined. Taste as you go.
3. If you want it to be sweeter, add ¼ of a cup of powdered sugar at a time and mix to combine. Repeat until you reach your desired sweetness. If the frosting is too thick, you can add ½ tablespoon of milk at a time, mixing after each addition, until you reach your desired consistency.