If making homemade stock, combine shrimp shells, onion, green pepper scraps, garlic, celery, and bay leaves in a large pot with 2 quarts of water. Bring to a boil and simmer for 45 minutes.

Remove the stock from heat and strain to reserve 2 cups of rich shrimp stock.

In a heavy-bottomed pot over medium heat, warm the vegetable oil or lard until shimmering, about 1-2 minutes.

Gradually whisk in the flour, cooking constantly until it turns a deep, chocolate brown color, approximately 10 minutes.

Toss in the chopped celery, green bell pepper, and onion. Sauté for about 4 minutes until the veggies soften.

Stir in the garlic and cook for another 2 minutes.

Slowly add the prepared shrimp stock, stirring continuously until thickened.

Mix in the Cajun seasoning, celery seed, and sweet paprika. Taste and add salt as needed.

Fold in the shrimp, cover the pot, and let it simmer on low heat for 10 minutes.

Stir in chopped green onions and hot sauce. Serve hot over fluffy white rice!