Portuguese Eggs

• 4 hard-boiled eggs
• 75 g/3 oz butter
• salt

First make the sauce: melt the butter in a saucepan and stir in the flour. Cook for half a minute, stirring. Add the milk and stir continuously while bringing to the boil. Add the bay leaf and the slice of onion, and salt and pepper to taste. Leave the sauce to infuse while you get on with the eggs.

Set the oven to moderately hot (200°C, 400°F, Gas Mark 6) and heat the grill. With a sta