Heat the oil in a large heavy pot or Dutch oven
over medium heat. Whisk
in the flour and cook, stirring constantly, to make a fragrant, dark chocolate-colored roux
, 25 to 30 minutes.
Add the onions, bell peppers, celery
, Essence, salt, and pepper. Cook, stirring often, until the vegetables soften, about 4 minutes. Stir in the stock and crabs. Bring to a boil. Reduce the heat to medium-low. Simmer
, uncovered, stirring occasionally, for 1 1/2 hours.
Meanwhile, heat a large skillet over medium-high heat. Add the chopped and sliced sausage and cook, stirring often, until browned, about 5 minutes. Remove from the heat.
Stir the shrimp, crawfish, and cooked sausage into the gumbo
. Cook over medium-low heat until the seafood
is firm, about 10 minutes. Remove from the heat and let stand for a few minutes. Skim
any fat from the surface.
Stir the green onions
and parsley into the gumbo. Spoon the rice
bowls and ladle the gumbo on top. Serve hot.