In a large 8 qt, heavy-bottomed pot, begin by browning the andouille sausage over medium heat until it is browned on both sides. Once done, remove the sausage from the pot and set it aside.

Pour in the vegetable oil and add the flour to the pot. Stir continuously with a wooden spoon to create a roux, cooking it until it reaches a dark brown color reminiscent of milk chocolate. This process should take about 20-30 minutes, so keep stirring!

Once your roux is ready, add in the onions, bell peppers, and celery. Stir and cook the vegetables for about 5 minutes, then add the garlic and cook for an additional 30 seconds, allowing the flavors to meld beautifully.

Return the browned andouille sausage to the pot and cook for another 5 minutes, stirring occasionally to combine all those tasty ingredients.

Pour in the seafood stock and bring the mixture to a boil. Once boiling, lower the heat to medium-low and add the bay leaves, thyme, salt, cayenne, and Bayou City Seasonings. Let it simmer for 45 minutes, skimming any foam or oil that rises to the surface.

After simmering, stir in the gumbo file and continue to let it simmer for an additional 15 minutes, enhancing the gumbo's signature thickness and flavor.

Finally, add the green onions, crab legs, and shrimp to the pot. Cook for 5-7 minutes or until the shrimp are pink and opaque. Take a moment to taste your gumbo and adjust the seasoning if necessary.

To serve, garnish your gumbo with fresh parsley and additional green onions, and ladle it over a bed of fluffy white rice in shallow bowls.