Combine all ingredients in a stainless steel, glass or crockery bowl. Cover and refrigerate for at least 4 hours before serving. This recipe makes about 2 cups, or enough for 1 pound of boiled peeled shrimp or crawfish tails.
To serve mix the shrimp or crawfish with the sauce and divide among six or eight chilled plates that have been lined with chopped lettuce. Garnish with lemon wedges.
This sauce is also wonderful as a dip for raw or lightly steamed vegetables.