Place the oven shelf in the lower third of the oven with no shelf above.
Prepare the soufflé dish and its collar.
Cut a piece of grease proof paper, 20x 12 inches (51x 30 cm).in length. Fold in ½ along the length so it now measures 20 x 6 inches (51x15 cm) doubled.
Now Turn up a 1 inch (2.5 cm) fold along the length to stabilize the base of the collar.
Butter the dish and sprinkle the inside with some of the parmesan, tipping the dish from side to side to coat the base and the sides.
Empty out the excess cheese.
Tie the paper collar around the dish with the 1 inch folded bit around the bottom.
The paper will stand 2 inches (5 cm) above the rim of the dish.
Fix with string. Butter the inside of the paper.
The dish is now ready for the soufflé.
Place the broccoli in a pot with a little water and a pinch of salt. Place a lid on top and cook until the broccoli is tender, approx 8/10 minutes.
Prepare the eggs. Have a large bowl containing the egg whites ready. Separate the 2 extra eggs putting the egg whites in with the extra egg whites and the yolks into a small bowl.
When the broccoli is tender allow to cool and whiz in a food processor until a smooth puree.
For the sauce:
Place the butter, flour and milk into a small pot and whisk over a medium heat until you have a smooth paste.
Season with salt and pepper.
Place in a mixing bowl and add the cayenne, nutmeg, cheddar, Gruyere, And 1 tablespoon of parmesan.
Add the 3 egg yolks, broccoli and thoroughly mix together.
Whisk the egg whites until stiff peaks have formed.
Using a large metal spoon, stir 1 tablespoon of the egg whites into the broccoli, then empty the broccoli mixture into the egg whites and fold, using cutting and turning movements, until everything is well mixed.
Pour the mixture into the prepared dish, sprinkle the top with the remaining parmesan and place on a shelf in the lower part of the oven for 40/45 minutes.