Place a 12-inch cast iron pan in the oven and preheat to 425 degrees.

In a large bowl whisk together the cornmeal, flour, baking powder, baking soda, and salt.

Make "vegan buttermilk" by combining the milk and vinegar in a medium-size bowl. Set aside. Place 4 tablespoons of the butter in a mug or small bowl. Microwave for about 15 seconds or until just melted.

Add the melted butter, maple syrup, and oil to the buttermilk, and whisk to combine. Pour wet ingredients into the dry ingredients, and whisk or stir just until there is no visible dry flour. The batter will look a bit lumpy.

Carefully remove the hot skillet from the oven and add the extra tablespoon of butter. Again, carefully (remember to put on your oven mitt before grabbing the handle) tilt the pan to swirl the butter around so it coats the bottom. Immediately pour the batter into the pan. Bake for 19 to 23 minutes. Use a toothpick or knife inserted in the center to test for crumbs/doneness.

Let the cornbread to cool in the pan for 20 minutes before slicing.