Step 1 Heat milk in saucepan over medium heat until bubbles form around edges. Stir in polenta and cornmeal and whisk until thickened, about 3 to 4 minutes. Cool about 10 minutes, then stir in egg yolks, butter, salt and baking powder.
Step 2 Beat egg whites with sugar until stiff, 2 to 3 minutes. Lightly fold half egg white mixture into polenta. Fold in remaining egg white mixture. (Always add egg white in 2 or more steps to evenly incorporate). Pour polenta mixture into well-oiled 2-quart baking dish or souffle dish. Bake at 350 degrees until polenta is puffy and browned, 45 to 50 minutes.