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

In a medium sized microwave safe bowl, or in a saucepan set over low heat, melt the butter, then add the sugar and stir to combine. return the mixture to the heat (or microwave) briefly, just until its hot (About 110°F to 120F), but not bubbling; it will become shiny looking as you stir it. Meeting this mixture a second time will dissolve more of the sugar, which will yield a shiny top crust on your brownies.

While the sugar heats a second time , crack the 4 eggs into a bowl , and beat them with the cocoa, salt, baking powder, espresso powder, and vanilla till smooth.

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

Add the flour and chips, again stirring until smooth. Note: if you want the chips to remain intact in the baked brownies, rather than melting in, let the batter cool in the bowl for about 20 minutes before stirring in the chips.

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. The brownies should feel set on the edges, and the center should look very moist, but not uncooked. Remove them from the oven and cool on a rack before cutting serving.