Preheat a 25cm (base measurement) heavy skillet or frying pan over medium heat. Spray the base and side with oil.
Combine the flour, polenta, sugar, baking powder and salt in a large bowl. Make a well in the centre and pour in the buttermilk, stock and butter. Add the egg and corn and stir until just combined.
Pour the mixture over the base of the skillet and spread to the edges. Reduce heat to low. Cover and cook for 20-25 minutes or until cooked through and set.
Preheat grill on medium-high. Drizzle the cornbread with extra butter. Cook under grill for 1-2 minutes or until golden. Set aside for 5 minutes to cool slightly. Cut into wedges and top with parsley.