Start by preheating your oven to 350°F (175°C). This ensures an even bake for your brownies.
In a medium saucepan over low heat, combine the salted butter and semi-sweet chocolate chips. Stir continuously until melted and smooth. Remove from heat and let it cool slightly.
Once the chocolate mixture has cooled a bit, whisk in the granulated sugar, vanilla extract, and instant coffee granules until well combined.
Add the eggs one at a time, mixing well after each addition to ensure they are fully incorporated into the batter.
In a separate bowl, whisk together the all-purpose flour, cocoa powder, and baking powder. Gradually add this dry mixture to the chocolate mixture, stirring until just combined. Be careful not to overmix!
Gently fold in the broken graham cracker pieces and Hershey chocolate bar until evenly distributed throughout the batter.
Pour the brownie batter into your prepared skillet, spreading it evenly across the bottom.
Dollop the marshmallow fluff over the brownie batter. Use a spatula to swirl it in slightly, creating a marbled effect.
Place the skillet in the preheated oven and bake for about 25-30 minutes, or until the edges are set but the center remains soft and gooey.
Allow the brownies to cool in the skillet for 10-15 minutes. Serve warm, straight from the skillet, and enjoy the gooey goodness!
