Preheat the oven to 400 degrees F. Grease the cups of a 12-cup muffin pan.
In a medium bowl, whisk the flour, cornmeal, sugar, baking powder, baking soda and salt. Stir the milk, egg and butter in a bowl. Fold in the scallions, 1 cup cheese and jalapenos, if using. Combine with the dry ingredients. Do not overmix (a few lumps are OK) or the muffins will be tough.
Fill the muffin cups 2/3 full. A 1/4 cup scoop makes the correct amount for each muffin as well as making filling the muffin cups go very quickly. Top with the remaining 1/4 cup cheese. Bake in the oven until a toothpick inserted into the center of each muffin comes out clean, about 18 to 20 minutes.
Remove from the oven and cool in the pan for 5 minutes. Remove from the pan and cool on rack.
See a picture of the muffins on Cooking.com: http://www.cooking.com/recipes-and-more/recipes/cheddar-scallion-muffins-recipe#ixzz3eaqgIJE3