Bite-savory pancakes won't last long at cocktail hour.
Combine milk and lemon juice in a bowl. Let stand until milk curdles and thickens, about 5 minutes. In a large bowl, combine flour, cornmeal, salt, baking powder, baking soda, and zest. Make a well in the center and pour in milk mixture, eggs, and oil. Stir just until combined; fold in blueberries and corn. Let batter rest 10 minutes.
Preheat a griddle or large skillet, preferably cast iron, over medium heat. Brush griddle with oil. Place a sage leaf on griddle and pour a level tablespoon batter directly over it. Repeat with remaining sage leaves and batter, leaving 1 inch between each cake. Brush griddle with oil between batches.
Transfer cakes to a cooling rack until ready to serve. Top each cake with 1/4 teaspoon sour cream, a blueberry, and a strip of zest.