I know there are plenty of people who will swear to using only soft wheat flour, like White Lilly Flour, or pastry flour, or some kind of mixture of both. I prefer to use a mix of cake flour and all-purpose flour. All-purpose flour gives biscuits a great structure and consistency, and a touch of cake flour keeps them nice and tender. Having said that, if you don't have cake flour, don't sweat it. Just omit the cake flour and use 2 3/4 cup all-purpose flour instead.