Begin by preheating your oven to 350ºF (175ºC). This ensures that your brownies will cook evenly. While the oven heats, you can set up the baking pan.

Line an 8x8 inch square baking pan with parchment paper. This makes removing the brownies after baking much easier. Don't forget to spray the pan lightly with non-stick cooking spray, ensuring every last crumb releases nicely.

Grab a large mixing bowl, and in it, combine the eggs, melted butter, and buttermilk (or milk). Give it a whisk until everything is well-blended.

Next, add the brownie mix and cocoa powder into that bowl. If you’re using espresso powder for added richness, toss that in as well. With an electric mixer on low speed, beat the mixture just until it’s combined—about a minute should do. It will be thick and luscious!

Add the chocolate chips and stir gently with a spatula until they're evenly distributed throughout the batter. Those tiny morsels will create pockets of delicious melted chocolate.

Pour the brownie batter into the prepared baking pan. Use your spatula to spread it evenly. Don’t worry about being too precise—these brownies are meant to be enjoyed, not perfectly arranged.

Place the pan in the preheated oven and bake for 37-40 minutes. A toothpick inserted in the center should come out with a few moist crumbs but not wet batter. Remember, the brownies will continue to set as they cool.

Once baked, remove the brownies from the oven and let them cool in the pan for about 10-15 minutes. Grabbing the edges of the parchment paper, lift the brownies out and let them cool completely on a wire rack. Slice into squares and get ready for the compliments!