Preheat the oven to 350°F. Lightly grease a 9"x 13" pan

Crack the 4 eggs into a bowl, and beat them at medium speed with the cocoa, salt, baking powder, espresso powder (if using), and vanilla for about 1 minute, or until smooth. You can do this while you're melting your butter (next step).

Melt the butter, then add the sugar and stir until well combined Continue to heat (or microwave) briefly, just until the mixture is hot but not bubbling; it'll become shiny looking as you stir it. Heating the mixture to this point will dissolve more of the sugar, which will help produce a shiny top crust on your brownies.

Add the hot butter/sugar mixture to the egg/cocoa mixture, stirring until smooth.

Add the flour and chips, stirring until smooth. Again, adding the chips helps produce a shiny top crust.

Bake the brownies for 28 to 32 minutes Remove them from the oven and cool on a rack before cutting and serving.