Preheat oven to 400°F (200°C) and adjust rack to the middle position.

Grease a 12-cup muffin tin.

Chop bacon into fine pieces.

Slice scallions thinly.

Fry bacon in a skillet over medium-high heat until crisp, about 5 minutes.

Stir in scallions, 1/4 teaspoon salt, and 1/8 teaspoon pepper.

Cook until scallions are heated through, about 1 minute.

Transfer bacon mixture to a paper-towel lined plate to cool.

In a bowl, whisk together flour, cornmeal, baking powder, baking soda, and 1/2 teaspoon salt.

In another bowl, whisk together sour cream, milk, sugar, melted butter, and eggs until combined.

Gently fold the sour cream mixture into the flour mixture with a rubber spatula until just combined. Do not overmix.

Gently fold in the bacon mixture and 1 1/2 cups of shredded cheddar cheese.

Using a greased 1/3 cup measure, portion the batter into each muffin cup.

Sprinkle the remaining 1/2 cup cheddar over the tops of the muffins.

Bake until golden brown and a pick comes out with just a few crumbs attached, 15-20 minutes, rotating the pan halfway through the baking.

Let the muffins cool in the pan for 5 minutes, then turn out onto a wire rack.

Let cool for 10 minutes before serving.