Step 1: Preheat your oven to 350°F (175°C) and line an 8×8 inch square baking pan with parchment paper, leaving an overhang on the sides.
Step 2: In a large bowl, whisk together the melted butter and granulated sugar until well combined and slightly grainy.
Step 3: Add the eggs one at a time, whisking vigorously after each addition until the mixture becomes pale and fluffy.
Step 4: Stir in the vanilla extract and espresso powder until fully incorporated into the base of your sinister blackout brownies.
Step 5: Sift the black cocoa powder, flour, and salt over the wet ingredients to prevent any lumps.
Step 6: Gently fold the dry ingredients into the wet mixture using a spatula until just combined; do not over-mix.
Step 7: Fold in the dark chocolate chips evenly throughout the batter.
Step 8: Pour the batter into the prepared pan and smooth the top with a spatula.
Step 9: Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Step 10: Remove from the oven and allow the sinister blackout brownies to cool completely in the pan before slicing.