Preheat the oven to 325 F, and place the rack in the top third of the oven. Grease a 12 cup muffin pan (do not use paper liners). Set aside.

Whisk together the flours, oats, baking powder, salt, ground flax, chia seeds, and walnuts or pecans. Set aside.

Melt the butter and coconut oil over low heat on the stove. Add the maple syrup and sugar and whisk together. Do not let the mixture get super hot. Remove the melted mixture from the stovetop and mix in the vanilla and maple extract. Let it cool until you can dip a finger into it without it hurting. Pour over the oat and flour mixture and mix gently. Add the eggs and mix quickly but gently until it is thoroughly mixed.

Scoop the mixture into the muffin cups--use all of it, it will come close to filling the cups. Sprinkle the coarse sugar over the dough. Bake for 25-30 minutes, until the cakes are golden all over and deeply golden at the edges. Let cool for 5 minutes, and then turn out onto a cooling rack to cool completely--if necessary, run a knife around the edges of the cakes to loosen them. The oat cakes will keep for a week in a sealed container.