Whisk together the melted butter, brown sugar, and granulated sugar.
Add in the eggs one at a time and whisk each one until fully incorporated and the batter starts to get lighter in color.
Then add in the brewed espresso and vanilla extract and mix until smooth.
Fold in the cocoa powder, flour, espresso powder, and salt and mix until the batter is just combined.
Cut a parchment paper sling slightly smaller than the width of the cake pan and make sure it fits flatly in the bottom. Then lightly spray the bottom and sides of the pan with a vegetable oil based spray. Place you parchment paper sling in the bottom of the pan and smooth it out so that it sticks to the pan spray (you can use metal binder clips to secure it to the pan).
Pour the batter into your prepared baking pan.
Bake at 350°F for 30-45 minutes or until an inserted knife comes out mostly clean.
Remove from the oven and let fully cool in the pan. Then use the edges of the parchment paper to slide the brownies out of the pan.
Brownies are best eaten within the first 2-3 days, but will keep in an airtight container at room temperature for up to 5 days.
It's better to undercook the brownies slightly, than overcook them! Brownies will dry out quick, so it's best to err on the side of caution when baking brownies! Bake just until an inserted toothpick comes out mostly clean but still a tad gooey. If you aren't sure, just go ahead and take them out because they'll continue to firm up as they cool. Note: the larger the pan, the less time the brownies will take to cook.Be patient and let them cool. Warm brownies fresh out of the oven are delish, I know. But it's best to let them fully cool before digging in. The brownies will be less likely to crumble when you cut them and the center is more likely to be fully cooked while still being perfectly fudgy.