Grease a muffin tin with a little butter or rapeseed oil. Cook the mushrooms and season. Add the onion and lardons, cooking for a minute or so. Put the mushrooms, lardons and onion to one side.
Meanwhile, break the eggs into a large bowl. Add salt and a sprinkle of freshly ground pepper. Add the cheese, yogurt, thyme, and nutmeg. Stir to combine, then add in the mushrooms, lardons and onion, and incorporate well. Sprinkle a little more cheese o top if desired.
Pour into the greased muffin tray, and cook in a 190 degree oven until just set. This varies between different ovens and muffin trays, but around 15 minutes. Check at 12 minutes.
When cooked, enjoy hot on buttered wholemeal English muffin halves, or any carb wholegrain source of your choice.
Extra cakes can be served with salad as a lunch, or eaten as a snack.