Melt margarine over low heat. Add finely
chopped onions and cook until onions are clear. Add 2 cups of
tap water and bring to a boil. Add crawfish tails and onion
tops and cook over low heat for 5 minutes, stirring occasionally.
Add seasoning to taste. Dissolve corn starch in 1/2 cup water
and pour into gravy. Allow to simmer for 15 minutes, stirring
occasionally. Remove from heat. Sprinkle parsley on
etouffee, stir then let set for a few minutes. Serve over