1. Butter four 3½” ramekins using a small pastry brush then line each with a layer of dry breadcrumbs. Chill in the refrigerator.
2. Pre-heat the oven to 135°C.
3. Separate the eggs.
4. Heat the milk in a saucepan with onion studded with clove and bay leaf.
5. Remove from heat, cover with a lid and allow to infuse.
6. Make a roux by melting 30g of butter in another saucepan and stir in the flour. Cook over a low heat for five minutes.
7. Stir in English mustard powder.
8. Strain and reheat the milk, then add to the roux, one ladle at a time, stirring well and allowing to almost boil between each addition.
9. When all of the milk has been added and the mixture is smooth, move to a low heat and allow to cook out gently for 5mins stirring regularly.
10. Remove from the heat and stir in the egg yolks and 100g grated cheddar cheese, then cover the pan with cling film to retain the heat.
11. Heat the remaining 10g butter until ‘nut brown’ in a non-stick frying pan and sauté spinach very briefly until it has wilted.
12. Season the spinach with salt and pepper then drain in a colander.
13. Transfer the spinach to a cutting board, chop coarsely with a large knife then stir into the cheese sauce.
14. Whisk the egg whites until they begin to thicken adding a tiny pinch of salt
15. Continue whisking until quite firm (beware of graining and drying out)
16. Beat a third of the whites into the cheese sauce with a wooden spoon then fold in the remainder very carefully using a rubber spatula.
17. Divide the mixture evenly between prepared soufflé moulds and sit the moulds in a tray of hot water. Transfer to the oven and bake for 25 minutes.
18. Remove the tray from the oven and allow to cool for 5 minutes, increase oven to 200°C.
19. Turn out the soufflés into four individual buttered oven-proof dishes and pour the double cream equally between them and scatter over the remaining grated cheese.
20. Return to the oven and bake for another 12 minutes or until almost doubled in size and golden on top.
21. Serve immediately.