Preheat the oven to 375°F (190°C). Line a 12-cup muffin pan with paper liners or lightly grease the cups with non-stick cooking spray.
In a medium mixing bowl, whisk together the flour, cornmeal, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar. Mix in one egg at a time until smooth and well combined.
Mix in ⅓ of the dry ingredients and then ½ of the milk, alternating between the two. Make sure to start and end with the dry ingredients. Use a rubber spatula to gently fold the batter together until just combined, leaving a few streaks of flour.
Fold in the blueberries and corn kernels, being careful not to overmix.
Divide the batter evenly among the prepared muffin cups, cavities should be very full. Make a 13th and 14th muffin if necessary to use up the batter. Sprinkle the tops with coarse sugar if desired.
Bake for 20–24 minutes, or until the tops are lightly golden and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Let the muffins cool in the pan for 5 minutes, then transfer them to a wire cooling rack to cool completely before serving.