Heat the butter or oil in a heavy casserole and saute the veal pieces lightly for a few minutes. Add the onions and continue to saute, stirring, until they are translucent. Pour in the wine and when it comes to a boil, add the chervil, a little salt and pepper, and 1/4 cup of broth.
Simmer, covered, very gently for about 50 minutes, or until the veal is tender. Check, and if more liquid is needed during the cooking, add a little more broth. When done, stir in the cream. Meanwhile, cook the fiddleheads in 1 quart of boiling salted water for 5 minutes, or until almost tender.
Drain, mix gently into the veal, and simmer about 3-4 minutes more. Taste and correct the seasoning, if necessary. Serving Ideas : Serve with rice, orzo, or steamed new potatoes.