Step 1: Preheat your oven to 350°F (175°C).
Step 2: Line a 9x9 inch baking pan with parchment paper and grease it lightly.
Step 3: Melt the unsalted butter in a medium saucepan over low heat and let cool slightly.
Step 4: Stir in the granulated sugar and espresso powder, then add the eggs and vanilla extract.
Step 5: In a separate bowl, whisk together the cocoa powder, flour, baking powder, and salt. Gradually add to the wet ingredients.
Step 6: Fold in the chocolate chips.
Step 7: Pour the batter into the prepared pan and bake for 20-25 minutes.
Step 8: Cool in the pan for 10 minutes, then lift out using the parchment paper and cool completely before slicing.
