Preheat oven to 190°C. Coat a medium round casserole dish with vegetable oil.
In a small saucepan, bring 1½ cups water and the polenta to the boil. Lower heat. Simmer, stirring frequently, 3 minutes. Transfer to a medium bowl. Place milk, salt, butter, chillies, capsicum and corn in the pan; heat until butter melts. When cool, stir in lightly beaten egg yolks.
Beat egg whites in a medium bowl until stiff peaks form. Fold into polenta mixture. Pour into prepared casserole.
Bake until centre is firm and top is browned, 50 minutes. Serve at once.