Preheat oven to 325 degrees F. Grease an 8-inch square metal or glass pan and line with parchment.
Cut the butter into chunks, put it in the batter bowl and heat for 1 minute. Stir, then repeat heating at 30 second intervals until butter is completely melted. Add sugar to hot butter and stir well, then stir in cocoa. Heat for another minute, stirring ever 30 seconds, so that the batter is very warm.
Stir in the vanilla extract and the salt. Make sure the batter is warm rather than piping hot, then add the cold eggs, one at a time, beating after each egg is added. Add the flour and stir until it is fully blended, then beat for about 40 strokes (I do this with another Pampered Chef item, my beloved Spatula Scraper).
Spread batter in the pan and bake for 25 to 28 minutes. A glass pan might take up to 28 minutes, while a metal pan might take 25. When done, the batter will still look extremely fudge-y. The toothpick test is useless here, but if you have a meat thermometer you can stick it in and check for a temp above 190F.
Allow the brownies to cool for several hours, then loosen slightly from edges of pan. If you have time, I recommend giving them a good chill before slicing.
Notes
Adapted from Alice Medrich’s Best Cocoa Brownies recipe