Preheat oven to 200 degrees C. Grease a 20cm x 32cm glass dish.
Combine polenta, flour, sugar and bi carb in a large bowl. Add milk, melted butter and egg; whisk until well combined. Pour batter into the glass dish.
Bake in the preheated oven until a toothpick inserted into the centre comes out clean, 20 to 25 minutes. Turn oven off and leave bread inside for a golden brown finish, 2 to 3 minutes more.