I have found a 1970's chinese dim sum steamed cake recipe that calls for Swans Down cake flour (author says "no substitutions"). I cannot find Swans Down on any local grocery shelves, yet. Our local chinatown used to carry this product but I can't find it now. I have searched and found it online, mainly in the southern states. Is there something equivalent you think I might be able to use in its place (combination of ingredients to make) without compromise? Does Softasilk cake flour give the same results in cakes? Thanks!