Steam the nettles for at least 5 minutes or until thoroughly wilted, work in batches if you steaming pot is small. Alternately blanch the nettles in boiling water for a few seconds, resulting in a slightly less “nettle-y” tasting, but still excellent frittata.
Finely chop the nettles and mix while still warm with the butter, cream, salt, pepper and nutmeg. Work in the eggs. The mixture will look stiff-don’t worry.
Taste a tiny pinch of the mixture again (if you’re wary of tasting uncooked eggs just skip it) adjust the seasoning until it tastes good to you.
Meanwhile, heat an 8 inch cast iron skillet with the oil until nearly smoking. Preheat the oven to broil.
Mix the nettle mixture quickly, then transfer to the hot pan, packing it down. Using a large spoon, press the edges away from the pan (see picture). Cover the frittata, turn the heat to medium, and cook for 5 minutes.
After five minutes, remove the lid, sprinkle on the parmesan, and place under the broiler for 5-10 minutes, or until the cheese is melted and the frittata is lightly puffed in the center.
Allow the frittata to cool for ten minutes to allow the flavor of the nettles to develop, then gently cut wedges from it, and serve. It’s great with a little tomato sauce on the side.