Salt, pepper, cayenne, file powder or other favorites, to taste (the Boudin Shop's exact mixture is secret)
Make a roux by combining the oil or lard and flour over medium heat
and stirring constantly. After about 15 minutes, the mixture will
begin to darken and become stronger in flavor. It begins to reach
readiness when the color becomes a milk-chocolate brown; a darker
color brings a more robust flavor.
Once your roux is a suitable color, add the onions, bell pepper
and celery. Add the water slowly, bring mixture to a boil, then
simmer 1 hour. Add seasonings to taste, then add the shrimp and
crawfish. Bring to boil again for 15 minutes.