If you use a non-stick pot that is about 8 or 9 inches around, you can even bake the brownies right in there! Otherwise, use an 8-inch square cake pan.
Preheat your oven to 325 degrees. If you are using a non-stick, oven-safe pot to mix and bake in, there's no need to grease a baking dish. If not, grease an 8-inch cake pan, round or square. Set aside.
In a medium pot, about 8-9 inches in diameter if you are baking in the pot, melt the butter and unsweetened chocolate over medium heat until smooth.
Remove from the heat. Stir in the sugar, eggs, and vanilla extract until combined. Then, add in the flour, cocoa powder, salt, espresso powder, chocolate chips, and chopped pecans. Stir until just combined. Pour the batter into your baking dish if using. Otherwise, place the pot directly into the oven, and bake for 35-40 minutes, or until a toothpick placed about two inches from the side of the pan comes out clean. Cool and enjoy!