In a heavy saute pan, cook vegetables in butter until soft, about 8-10 minutes. Add three shakes Worcestershire sauce and 1 tablespoon lemon juice.
Add Cajun spices to taste and saute about 1 minute. Add crawfish and continue to saute on low heat another 15 minutes; add heavy cream. Saute until reduced by half; adjust seasonings. Spoon over (cooked) fish.