Adjust oven rack to middle position and heat oven to 400 degrees. Generously spray 12-cup muffin tin, including top, with vegetable oil spray. Whisk flour, 1 cup cornmeal, sugar, salt, baking powder, and baking soda together in large bowl; set aside.

Whisk milk and remaining 1/2 cup cornmeal together in medium bowl. Microwave until mixture begins to thicken to paste-like consistency, 1 to 3 minutes, whisking frequently. Whisk sour cream and melted butter into cornmeal paste. Whisk in eggs. Stir cornmeal mixture and corn kernels into flour mixture until just combined.

Using greased 1/3-cup dry measuring cup or #12 portion scoop, divide batter equally among prepared muffin cups; evenly distribute any remaining batter among cups (cups will be full).

Bake until muffins are golden brown and toothpick inserted in center comes out with few crumbs attached, 20 to 24 minutes. Let muffins cool in muffin tin on wire rack for 5 minutes. Remove muffins from muffin tin and let cool on rack for 15 minutes. Serve warm.