Preheat oven to 425ºF. Grease a 12-cup muffin tin.
In a medium bowl, whisk together 1½ cups of the cornmeal, flour, parmesan cheese, baking powder, baking soda, salt, sage and pepper.
In a large bowl, whisk together the remaining ½ cup cornmeal and milk. Microwave on high for 1½ minutes, then whisk thoroughly. Continue to microwave, whisking every 30 seconds, until thickened to a batter-like consistency; about 3 minutes.
Whisk in the sour cream, melted butter, and sugar until combined, then whisk in the eggs. Fold in the flour mixture and green onions (if using) until thoroughly combined (batter will be very thick). Divide batter evenly among the prepared muffin cups (the batter will mound slightly above the rim).
Bake until the tops are golden brown and a toothpick inserted in the centre comes out clean, 13 to 17 minutes, rotating the muffin tin halfway through baking.