Working in a large bowl, whisk together the flour, cornmeal, sugar, baking powder, baking soda, salt and nutmeg. In a large glass measuring cup with a spout or in another bowl, whisk together the buttermilk, melted butter, oil, egg and yolk. Pour the liquid ingredients over the dry ingredients and, with the whisk or a rubber spatula, gently but quickly stir to blend. Don't worry about being thorough – the batter will be lumpy and that's just the way it should be. Stir in the corn kernels. Divide the batter evenly among the muffin molds.