Preheat oven to 425°, with rack in upper third. Butter 24 mini muffin cups; set aside.
In a medium bowl, whisk together flour, cornmeal, sugar, baking powder, salt, and baking soda.
Make a well in center of flour mixture. In well, whisk together egg, sour cream, and corn. Mix with flour mixture just until incorporated (do not overmix).
Dividing evenly, spoon batter into prepared muffin tin. Bake until tops have browned and a toothpick inserted in the center of a muffin comes out clean, 10 to 15 minutes. Let stand 5 minutes in pan; turn out onto a cooling rack. Serve, or cool completely and store at room temperature in an airtight container, up to 2 days.
NOTE: Can also be made in a standard 12-cup muffin tin. Bake 15 to 20 minutes.