Spray an 8-by-8-inch baking pan with nonstick spray. In a large bowl, whisk together 1/3 cup water and the oil, egg and espresso powder. Add the brownie mix and stir until well blended. Stir in the peanut butter chips. Transfer the batter to the prepared baking pan. Sprinkle the salt evenly over the top. Bake until a toothpick inserted into the center of the brownies comes out with a few moist crumbs attached, 35 to 40 minutes. Cool completely before cutting into squares. Arrange the brownies on a platter and serve.