Cajun Chicken, Sausage, and Oyster Gumbo

The depth of flavor in slowly cooked Cajun dishes comes partly from a Cajun brown roux, which is cooked very dark, almost burnt, so that most of the flour’s thickening power has been fried out of it. The roux gives a little body, but mainly it gives a mysteriously delicious, muddy richness, which is one of the things that sets this gumbo apart from anyt…