Preheat the oven to 350°F. Lightly grease a 9" x 13" pan., Combine the melted butter and sugar, stirring until smooth., Stir in the cocoa, salt, baking powder, vanilla, and espresso powder., Beat in the eggs one at a time. Scrape the bowl, then add the water, stirring until smooth., Add the flour, nuts, and chips, stirring until thoroughly combined., Spoon the batter into the prepared pan., Bake the brownies for 28 to 30 minutes, until a toothpick inserted into the center comes out clean, or with a few moist crumbs attached. The brownies should feel set both on the edges and in the center., Remove the brownies from the oven, and cool them on a rack before cutting and serving. Glaze or frost, if desired.