Sift the flour, baking soda, and salt together in a medium bowl. In another bowl or a liquid measuring cup, whisk together the hot water, cocoa powder, and espresso powder until smooth. Add the half-and-half and whisk until smooth. With the mixer on low, add the flour and chocolate mixtures alternately in thirds, starting and ending with the flour. With a rubber spatula, scrape down the bowl to be sure the batter is well mixed.