In a large bowl, stir together the flour, cornmeal, baking powder, baking soda, and salt until well mixed. In a small bowl, whisk together the butter and sugar until it forms a thick slurry. In a second large bowl, whisk the eggs until well blended. One at a time, whisk the milk, then the oil then the crme frache, and finally the butter-sugar slurry into the eggs. Pour the wet mixture into the dry mixture and fold carefully just until the dry and wet ingredients are well combined. The batter will the thick and pasty.