1 large egg, lightly beaten, mixed with 1 tablespoon water
Preheat oven to 425°F. Lightly oil a baking sheet or coat it with cooking spray.
Stir together flour, cornmeal, sage, baking powder, sugar, baking soda and salt in a mixing bowl. Cut in cream cheese and butter with two knives or your fingers until you have lumps the size of peas. Stir in buttermilk until just combined. Do not overmix or the biscuits will be tough.
Turn the dough out onto a floured surface and pat into a circle about 9 inches in diameter. Cut into 12 wedges with a sharp knife. Transfer the wedges to the prepared baking sheet. Brush them lightly with some of the egg mixture. Bake until they are firm to the touch and very lightly browned, 10 to 12 minutes. Serve warm.