Begin by dicing the onion and peeling the shrimp, reserving the shells. Place the peeled shrimp in the refrigerator until ready to use.
Prepare the shrimp stock by heating olive oil in a pan over medium heat. Add the shrimp shells, including the heads, and bay leaves. Sauté for 3-4 minutes until fragrant. Pour in the chicken broth, reduce the heat to low, and let it simmer while you prepare the crabs.
While the shrimp stock simmers, bring a pot of water to a boil. Add the live crabs and boil them for 3-5 minutes. Drain and let them cool.
Clean the blue crabs by removing the large claws, top shell, gills, and apron. Set aside the large claws and cleaned gumbo crabs to be added later.
Blend one can of tomatoes and set aside.
Stir the shrimp stock and press down on the shells to extract the juices. Strain the shrimp stock, ensuring to remove all shells. Set aside both the tomato sauce and seafood broth for later use.
In a large pot or dutch oven, combine Bisquick and oil to make the roux. Stir continuously over medium-low heat until the roux reaches a dark chocolate color, approximately 20-30 minutes. Do not leave the roux unattended to prevent burning. Add the finely chopped onion when the roux turns dark brown.
Quickly pour the seafood broth and blended tomatoes into the roux. Add the sliced okra and crabs. Hand-squeeze the remaining can of tomatoes and add them to the gumbo along with the tomato sauce. Season with salt, pepper, and your favorite Cajun seasoning. Cook on low heat for 20-30 minutes, adding water if needed to adjust the consistency.
During the last 5-10 minutes of cooking, add the seasoned shrimp and jumbo lump crab meat. Cook until the shrimp are pink and fully cooked.
Serve the classic seafood gumbo warm. Optionally, serve it with rice. Garnish with fresh parsley. Enjoy!