01 -
Position your oven rack in the lower third of your oven. Preheat oven to 325ºF. Line an 8-inch square pan with parchment or aluminum foil and spray lightly with non-stick cooking spray.
02 -
In a large glass bowl, combine butter, sugar, cocoa powder, and salt. Place the bowl over a pan of barely simmering water. Stir occasionally until the butter is melted and the mixture is combined.
03 -
Remove the mixture from heat and allow to cool for 5-10 minutes. Ensure the mixture is not too hot before adding eggs.
04 -
After cooling slightly, add vanilla extract and mix well. Add the eggs one at a time, beating vigorously after each addition until very well mixed.
05 -
In a separate bowl, whisk together the flour and baking powder. Add the flour mixture to the batter and stir very well to combine, mixing about 40 strokes with a spoon.
06 -
If using chocolate chips or chopped walnuts, fold them into the batter.
07 -
Pour the batter into the prepared pan and bake for 30-35 minutes or until a tester inserted comes out with moist crumbs. Cool completely on a wire rack before serving.
08 -
Serve and enjoy. If not eating the same day, wrap or cover tightly for storage.