Turn the oven on to 150°C/Gas 2. Half-fill a roasting pan with water and place on the middle shelf of the oven to warm up. Butter a 1.2 litre ovenproof round dish.
For the custard, lightly whisk the eggs in a large bowl. Heat the milk in a pan to just below the boil, add the cheese and stir until smoothly melted in, then slowly whisk into the eggs. Grate the nutmeg onto the mixture and