Position oven rack in center of oven.
Preheat oven to 325ºF
Line a 8-inch square pan with parchment or alumni paper. Spray with non-stick cooking spray, then set aside.
Place butter in a large, microwave-safe bowl and heat for one minute. If butter is not fully melted after one minute, return to microwave and heat in 15 second bursts until fully melted. Remove bowl from microwave.
Add sugar, cocoa powder and salt to the melted butter and mix well to combine. The mixture will likely be dry, that's to be expected.
Allow mixture to sit for five minutes to make sure it has cooled prior to adding additional ingredients.
After mixture has cooled slightly, add vanilla and mix well.
Add room-temperature eggs, one at a time, mixing well after each egg is added. Once both eggs have been added, mix with an electric mixer on medium for 3-5 minutes.
In a separate bowl combine flour and baking powder, and stir to combine.
Add flour mixture to batter and mix by hand to combine. While we want to avoid over mixing, this batter does need to be stirred well to incorporate all the ingredients. Stirring about 40 strokes with a spoon is a good guide.
Fold chocolate chips (or nuts) into the batter and gently stir until combined.
Bake for 30 to 35 minutes, or until a tester comes out with some moist crumbs attached. Once the center has started to set up and no longer jiggles when you shake the pan, it's time for these brownies to come out to avoid over baking.
Allow to cool on a wire rack.
Serve warm or at room temperature and enjoy. If not eating the same day, wrap tightly with plastic wrap. Brownies will stay fresh for 3-4 days if well wrapped.