Step 1

Preheat oven to 190°C. Place a baking tray in oven. Grease a 1.5L (6-cup) capacity ovenproof dish with butter. Dust with breadcrumbs.

Step 2

Heat butter in a saucepan over medium heat until foaming. Cook flour, stirring, for 2 minutes or until it bubbles and comes away from the side.

Step 3

Remove from heat. Gradually whisk in half the milk until mixture is smooth. Gradually whisk in remaining milk until smooth and combined.

Step 4

Whisk over medium heat for 3-4 minutes or until sauce boils and thickens. Add cheddar and stir until cheddar melts and mixture is smooth.

Step 5

Remove the saucepan from heat. Quickly whisk in the egg yolks until well combined. Transfer the mixture to a large bowl. Use an electric beater to beat the egg whites in a clean, dry bowl until firm peaks form. Be careful not to overbeat the egg whites.

Step 6

Add one-third of egg white to cheddar mixture. Use a large metal spoon to fold. Repeat, in two more batches, with the remaining egg white.

Step 7

Spoon into prepared dish. Run your finger around the inside rim of the dish. Place on preheated baking tray. Bake for 25-30 minutes or until golden.