Method
Prep:25min  ›  Cook:45min  ›  Ready in:1hr10min 

1. Preheat the oven to 220°C/gas 7. Lightly oil a large ovenproof baking dish of about 2.4 litre capacity, then sprinkle the breadcrumbs around the inside of the dish.
2. Put the polenta in a large heatproof bowl and stir in the mustard, then pour in the boiling water and stir until smooth. Cool slightly, then stir in the egg yolks, sweetcorn, spring onions, chives and about 40g of the cheese. Add the buttermilk and stir to form a thick batter.
3. Whisk the egg whites in a separate bowl until stiff peaks form. Beat 1 large spoonful of the egg whites into the batter to lighten it, then fold in the remaining whites.
4. Spoon the mixture into the prepared dish and sprinkle the remaining cheese over the top. Bake for 40–45 minutes until the top is set and golden brown. Serve at once, straight from the dish.

Variations

Boost the vegetable content by adding diced steamed carrots, sliced leeks or frozen peas (no need to thaw).

Cook's tip

If you can't find buttermilk, you can substitute semi-skimmed milk mixed with 1 teaspoon lemon juice. Leave it to stand for 5 minutes before using.