If you’d like to make this cake using whole wheat flour then substitute the oat flour, rice flour, arrowroot powder, and xanthan gum with 1 cup plus 2 tablespoons whole wheat pastry flour. If you don’t have any maple sugar on hand, simply use a very dark brown sugar such as a muscovado. Also, if you are gluten free then substitute the stout for a dark gluten free beer such as Greens.
Inspired from Easy Desserts.