Let’s kick things off by preheating your oven to 350°F (175°C). Greasing your pan ahead of time ensures easy removal of those delicious brownies later. I usually use a 9×9-inch square pan, but an 8×8 works just fine too.

In a large mixing bowl, combine the softened butter, vegetable or coconut oil, and granulated sugar. Mix them together until creamy. It should come together beautifully, almost like a little cloud of sweetness! Then, add in the eggs and egg yolk. Beat them until fully incorporated, ensuring you’re creating a luscious mixture.

Now, here’s where the magic happens. Stir in the vanilla extract and optional espresso powder. The espresso powder is like a secret handshake for your chocolate. It’s not overpowering, but it helps those chocolate flavors shine brighter.

In a separate bowl, sift together the flour, cocoa powder, baking powder, salt, and cinnamon. This step isn’t just to avoid lumps; it’s about aerating the dry mix to create a light texture amidst the fudginess. Gradually add your sifted mix to the wet ingredients, folding it gently.

Once the batter looks fabulous, fold in the semisweet chocolate chips. You want to make sure they’re evenly distributed throughout the mix, giving every bite a gooey piece of chocolatey goodness.

Pour the brownie batter into your prepared pan and smooth it out evenly. Pop it into the oven and let it bake for around 25-30 minutes. Your kitchen will soon smell like a chocolate factory. Keep an eye on it, as you want the edges firm and the center slightly soft.

Once out of the oven, let the brownies cool in the pan for at least 15 minutes before transferring to a wire rack. This helps with cutting. You want those clean edges when slicing them into squares.