Special equipment: 2 well-seasoned cast-iron corn stick pans, each with 7 (5-by 1 1/2-inch) mold, or a well-seasoned 9-inch cast iron skillet.
Preheat oven to 425 degrees. Heat pans in middle of oven 10 minutes. Whisk together cornmeal, sugar, baking soda, and salt in a large bowl. Whisk together buttermilk and egg in another bowl and add cornmeal mixture with cheddar, scallion, jalapenos, and 2 tablespoons butter, stirring, until just combined. Remove pans from oven and divide remaining 2 tablespoons butter among corn stick molds. Quickly divide batter among molds (about 3 tablespoons each) and bake until a tester comes out clean and tops are golden, 12 to 15 minutes. Cool corn sticks in pans 3 to 5 minutes before removing from molds. Serve warm.
If using a cast-iron skillet, pour all of batter into it and bake 15 to 20 minutes.