Position a rack in the center of the oven, and heat the oven to 350° F.
Spray muffin liners with cooking spray and place in tray.
In a large bowl, stir together the cornmeal, flour, baking powder, baking soda, and salt until combined. In a separate bowl, whisk together the melted butter, oil and maple syrup until a thick slurry forms.
Whisk in the eggs, one at a time, and then whisk in the buttermilk and sour cream.
Pour the wet egg mixture into the cornmeal mixture, and then, using a rubber spatula, fold together until all of the cornmeal is completely incorporated.
Fold in the corn kernels and the sage until they are evenly distributed throughout the batter.
The batter will be thick and pasty.
Fill muffin cups half full.
Bake for 20 to 30 minutes, or until the tops are light golden brown and a toothpick inserted in the center comes out clean.
Let cool completely in the pan on a wire rack.
The corn bread can be stored, tightly wrapped in plastic wrap, at room temperature for up to 2 days or in the freezer for up to 2 weeks.
If muffins have been frozen, put them directly into the oven for 15 to 18 minutes at 300° to thaw.