In a bowl, mix cornmeal, flour, sugar, baking powder, and salt. Stir in milk, oil, and egg; beat just until well blended. Pour batter into a buttered 8-inch square pan. Bake in a 425° oven until golden brown and edges just begin to pull from pan sides, about 25 minutes. Let cool at least 10 minutes. Use, or cool, cover, and store at room temperature up to 1 day. Cut into 3/4- to 1-inch chunks.