Preparation Put oven rack in middle position and preheat oven to 450°F. Butter 1 large baking sheet. Whisk together flour, cornmeal, baking powder, baking soda, and salt in a bowl, then blend in butter with your fingertips or a pastry blender until mixture resembles coarse meal. Stir in cheeses and scallions with a wooden spoon, then add buttermilk and stir until just combined. Drop dough in 8 equal mounds about 2 inches apart on baking sheet. Bake until golden, about 15 minutes. Transfer to a rack and cool to warm, about 10 minutes, then cut in half horizontally. Cooks' notes:You can use 2 small baking sheets instead of 1 large. Bake biscuits in upper and lower thirds of oven, switching position of sheets halfway through baking. Biscuits can be made 1 day ahead and cooled completely, then kept in an airtight container at room temperature. Reheat in a preheated 350°F oven 10 minutes.
Preparation Put oven rack in middle position and preheat oven to 450°F. Butter 1 large baking sheet. Whisk together flour, cornmeal, baking powder, baking soda, and salt in a bowl, then blend in butter with your fingertips or a pastry blender until mixture resembles coarse meal. Stir in cheeses and scallions with a wooden spoon, then add buttermilk and stir until just combined. Drop dough in 8 equal mounds about 2 inches apart on baking sheet. Bake until golden, about 15 minutes. Transfer to a rack and cool to warm, about 10 minutes, then cut in half horizontally. Cooks' notes:You can use 2 small baking sheets instead of 1 large. Bake biscuits in upper and lower thirds of oven, switching position of sheets halfway through baking. Biscuits can be made 1 day ahead and cooled completely, then kept in an airtight container at room temperature. Reheat in a preheated 350°F oven 10 minutes.