In a saucepan, scald the milk, heat to 180 degrees F; stir in cornmeal. Reduce heat; simmer for 5 minutes, stirring constantly. Remove from the heat; stir in butter, sugar, salt and baking powder. In a small bowl, beat egg yolks. Gradually stir a small amounts of the hot mixture into yolks; return all to pan and mix well. In a mixing bowl, beat egg whites until soft peaks form. Fold egg whites into hot mixture until well blended. Pour into a greased 8-in. square baking dish. Bake at 350 degrees F for 40-45 minutes or until well puffed. Use a spoon to serve.