Preheat oven to 220°C / 425°F (200°C / 390°F fan).
Put the spinach in a pan with the milk and bring to the boil, then remove from the heat.
Melt the butter in a large pan, stir in the flour using a sauce whisk and cook over a low heat for a minute or two – do not let it brown.
Add the spinach and milk, stirring constantly, and simmer until the sauce is thick and smooth.
Remove the pan from the heat, season with salt and pepper to taste, add the nutmeg and Comté, mix well and then stir in the egg yolks.
In a separate bowl, whisk the egg whites until they are stiff and fold them carefully into the mixture.
Butter 8 individual ramekin dishes or dariole moulds very generously, then spoon in the mixture (you may have enough mixture for 10 if your ramekins or moulds are small).
Place the ramekins into a roasting tin and gently pour boiling water into the tin until it comes half way up the outside of the ramekins.
Cook for 15 to 20 minutes until golden and springy to the touch.
Remove from the oven, but leave them in the roasting tin, and leave until the soufflés shrink back and are cold. Run a cutlery knife around each ramekin and turn the soufflés out, scraping off any bits of remaining soufflé and sticking them back onto the bottom of the soufflé. NB – you can wrap them in cling film and freeze them at this stage.
For the topping, generously butter a gratin dish that can hold the soufflés without them touching. Sprinkle half of the Comté over the base of the dish, put the soufflés in upside down (can be covered in cling film and left in fridge overnight at this stage, then brought up to room temperature before next stage), pour the cream over and sprinkle over the rest of the Comté.
Bake in the oven (same temperature as before) for another 15 to 20 minutes until they have puffed up and are golden brown, then serve straight away.