Excerpted from Flavor Flours by Alice Medrich (Artisan Books). Copyright © 2014. Photographs by Leigh Beisch. Oat Flour Sponge Cake Serves 8 to 10 Alice says, "Oat flour turns a plain-Jane sponge cake into something elegant with the subtle but distinct flavors of butterscotch or toffee. The crusty edges I picked off my first oat