Bring a pot of lightly salted water to a boil, then blanch the fiddleheads at a rolling boil for at least 1 minute, or until the texture is to your liking (no more than 2-3 minutes).
Remove the fiddleheads to a tray with a slotted spoon and spread them out to cool naturally.
Line the fiddleheads up and cut the stems into 1 inch pieces, leaving the crosiers (coiled top) whole.
Mix the cut stems and crosiers with the remaining ingredients, taste and double check the seasoning, then adjust as you see fit for acid, pepper, salt and herbs. It is nothing to taste the salad two, three, or four times to get the balance to your liking.
The salad can be made 15 minutes or so ahead of time, but will begin to discolor as the acid cooks the fiddles over time. To make it in advance, add all the ingredients, mixing in the lemon just before serving.
Variations and notes
Adding other shoots is great here: asparagus, swamp saxifrage, wood nettle, dames rocket, use your imagination. Fiddles are just one type of delicious shoot we have.
Add some small young greens like chickweed, watercress or others to make a larger salad.
If you want to make the salad in advance, leave out the acid and add it at the last moment before serving.
Don't forget the herbs. Herbs are part of what makes this exciting, use whatever you have, but try not leave them out since they help give it lift.