1) Preheat the oven to 350°F. Lightly grease a 9" x 13" pan, line it with parchment, and if desired grease the parchment — this makes it easier to remove the brownies from the pan.
2) In a medium-sized saucepan set over low heat, melt the butter, then add the sugar, stirring to combine. Heat the mixture briefly, just until it's hot throughout; it'll become shiny looking as you stir it — this will dissolve some of the sugar and yield a shiny top crust on your brownies.
3) Stir in the cocoa, salt, baking powder, espresso powder, cinnamon, and flavoring(s).
4) Whisk in the eggs, stirring until smooth.
5) Add the flour, again stirring until smooth.
6) Fold in the chocolate chips.
7) Spoon the batter into the pan, spreading it to the edges.
8) Bake the brownies for 34 to 36 minutes, until a cake tester inserted into the center comes out clean. The brownies should feel set on the edges, and just barely set in the center.
9) Remove from the oven and allow to cool completely in the pan before cutting.
Yield: about 24 brownies.