Preheat your oven to 325 degrees. Adjust your oven rack to the middle position. Grease your 9 inch springform pan with cooking spray or butter. Set aside.
You now have 2 options. 1) In a small saucepan, melt butter, over low heat. Add chocolate and stir until combined. OR 2) Using a small bowl or measuring cup melt butter and chocolate together in your microwave, on low, stirring every 30 seconds or so, until melted and totally blended together. Set aside to cool slightly.
In a medium to large mixing bowl, combine sugar, eggs, Kahlua, vanilla, baking powder, and salt. Use a whisk to mix the ingredients together. Add chocolate mixture and continue to whisk until smooth. Add flour and whisk until totally incorporated.
Next, dump your batter into your prepared springform pan. Do your best to spread the batter as evenly as possible across the bottom of the pan, trying not to get any brownie batter on the sides of the pan. You want the layers of this cake to be as perfect as possible!
Bake until top of brownie begins to crack and a toothpick inserted into the center comes out almost clean. A few crumbs are ok! It will take around 24 minutes. Sometimes a little less, sometimes a little more. I always rotate the brownies at about the 12 minute mark. Once brownies are cooked, remove them from your oven and place on a wire rack to totally cool.