Preheat oven to 325 degrees. Line a muffin pan with 12 paper liners and set aside.
In a large bowl, whisk all dry ingredients together, including sugars. Make a well in the middle of the dry ingredients. Pour remaining wet ingredients into the well of the flour. Slowly stir to incorporate. Spoon batter into prepared tins and top with chopped walnuts, if desired. Bake 15 minutes or until toothpick comes out clean after inserted. Serve warm with butter.