Preheat your oven to 350°F (175°C) to ensure even baking.
Line a 9x13-inch baking pan with parchment paper, allowing overhang for easy removal.
In a medium saucepan over low heat, melt the chopped semi-sweet chocolate and cubed butter until smooth. Remove from heat and let cool slightly.
In a separate bowl, whisk together the flour, salt, cocoa powder, and espresso powder. Set aside.
In a large mixing bowl, combine granulated sugar and lightly beaten eggs. Whisk until smooth and slightly pale.
Slowly add the melted chocolate and butter mixture to the sugar and egg mixture, stirring until fully combined.
Gently fold the dry ingredients into the wet ingredients using a rubber spatula until just combined.
Mix in the vanilla extract and chocolate chunks until evenly distributed.
Pour the batter into the prepared baking pan and spread evenly. Bake for 25-30 minutes, or until a toothpick comes out with a few moist crumbs.
Let the brownies cool in the pan on a wire rack. Use the parchment overhang to lift them out, then cut into squares and enjoy!
