Gather the ingredients.
Preheat the oven to 350 F and lightly grease an 8x8 or 9x9 pan.
Combine the butter and sugar in a medium heatproof bowl. Microwave in 30-second increments, stirring each time, until the butter is melted. Alternatively, stir in a pot on the stove over medium-low heat. Let cool a bit while you sift together the dry ingredients.
In a large mixing bowl, sift together the flour, cocoa powder, baking powder, and salt.
Add the butter and sugar mixture, eggs, vanilla, and espresso powder.
Mix together just until well-mixed.
Add the chocolate chips and mix until combined.
Scrape the batter into the prepared baking pan. Bake in the preheated oven for 20 to 25 minutes for a 9x9 pan or 23 to 30 minutes for an 8x8 pan, or until a toothpick inserted into the middle (avoiding a chocolate chip) comes out clean or with a moist crumb or two attached but no liquid batter.
Let cool completely. For very tidy-looking brownies, refrigerate the cooled brownies for about an hour before cutting with a sharp knife.
