Preheat the oven to 350°F. Line an 8-inch square metal pan with foil and spray the bottom with cooking spray.

In a medium size 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 briefly and heat just till it's hot (about 110°F to 120°F) but not bubbling. Don't worry if it separates; just stir it briefly to recombine a bit. Heating this mixture a second time will dissolve more of the sugar, which will yield a shiny top crust on your brownies.   Transfer the mixture to a bowl (or just let it cool slightly and do everything in the saucepan), and stir in the cocoa, salt, baking powder, espresso powder if using, and vanilla.

Add the eggs, stirring till smooth. Then add the flour and chips, again stirring till smooth. Spoon the batter into the prepared pan.

Bake the brownies for 27-30 minutes, until a cake tester or sharp knife poked into the center reveals wet crumbs, but not raw batter. The brownies should feel set on the edges and in the center. Remove them from the oven, and cool completely on a rack.  Cover and let sit overnight (I kept mine in the refrigerator, but served at room temp) before cutting and serving.

Yield: 1 dozen