Grind together crawfish tails, 1 onion, celery, bread (may use food processor).
Chop parsley and shallot greens.
Mix well in a large bowl, add seasonings, pepper, salt, add eggs, mix well. Add bread crumbs mix to form a dressing like consistency(this is the stuffing for the heads).
I fry my heads, but some people like to brown them in the oven(your choice).
Stuff heads with the mixture. Should stuff about 35 per pound.
After stuffing heads; pass in flour and fry in cooking oil until browned.
Set fried heads aside.
Make your roux using 1 cup flour and 1 cup oil. Brown 1 chopped onion in roux. Add fried heads to roux, add enough water to cover heads, about 3/4 to one inch above the heads. Cook on low heat for approximately 1hr, 45 minutes, add shallot greens and parsley(chopped), cook for another 15 minutes.