Preheat oven to 350°F and spray a 9-inch square baking pan lined with parchment paper for easy removal with non-stick cooking spray. Next decide if you want stovetop or microwave method, then move on to step 4.
Stovetop Method: In a medium saucepan, melt chocolate chips and butter over low heat. Then, let it cool slightly.
Microwave Method: Melt chocolate chips and butter in the microwave in a microwave safe bowl in 30 second increments stirring every 30 seconds until melted and let cool slightly.
Add sugar and vanilla to the mixture. Once it cools down, add eggs and mix it in.
In a separate bowl, mix together the cocoa powder, flour, baking powder, and salt in a bowl. Then, add the dry mixture to the wet mixture and whisk or stir together until combined well.
Add walnuts to the brownie batter and spread mixture evenly in your prepared pan.
Bake for 25-35 minutes or until a toothpick inserted into the center comes out clean. Let cool completely before cutting into squares. Depending on how fudgy you want the brownies, check at 25 minutes and go from there when you want to pull them out of the oven to cool. Brownies will continue baking once they are pulled from the oven, so keep that in mind as to not overbake the brownies.