Preheat the oven to 350°F. Lightly grease a 9" x 13" pan.
Crack the 4 eggs into a bowl, and beat them with the cocoa, salt, baking powder, espresso powder, and vanilla till smooth.
In a saucepan set over low heat, melt the butter, then add the sugar and stir to combine. Continue to heat, just until the mixture is hot, but not bubbling.
In the bowl of a stand mixer, pour in the butter mixture. Add the cocoa mixture, mixing until combined. Add the flour and chips, stirring until smooth.
Spoon the batter into a lightly greased 9" x 13" pan.
Bake the brownies for about 30 minutes, until a cake tester inserted into the center comes out clean, or with just a few moist crumbs clinging to it. Remove them from the oven and cool on a rack before cutting and serving.
by The Savvy Kitchen