Heat oven to 325 degrees. Line a shallow baking pan with a cloth towel, and set aside. Place cocoa powder in a medium mixing bowl. In another bowl, combine skim milk and evaporated milk. Slowly whisk about 3 tablespoons milk mixture into cocoa powder until it forms a thick paste. Whisk in remaining milk mixture until thoroughly combined, and set aside.
In a large bowl, combine eggs, egg white, granulated sugar, and salt, and whisk together until thoroughly combined. Whisk in cocoa-milk mixture until completely combined. Divide the mixture among six 3-ounce pot de creme molds or six 3-ounce ramekins, and place in the prepared baking pan; fill the baking pan halfway with hot water. Transfer to the oven to bake until the puddings are set and leave no residue on your finger when lightly touched, about 25 minutes. Remove the baking pan from the oven, then remove the puddings from the water bath. Transfer the puddings to a wire rack, and let cool 20 to 30 minutes. When ready to serve, dust the puddings with confectioners' sugar. Serve warm.