Prepare the roux by melting ½ cup of unsalted butter over medium-low heat. Whisk in ½ cup of all-purpose flour, stirring constantly for about 10 minutes until it turns a rich, caramel color.

Add 1 small diced yellow onion, 1 medium chopped green bell pepper, and 2 chopped celery stalks. Cook for about 5-7 minutes until vegetables are softened.

Mix in 12 ounces of sliced Andouille sausage and 2 minced garlic cloves. Sprinkle in 1 tablespoon of Cajun seasoning along with salt and pepper to taste. Cook for another 3-4 minutes.

Pour in 4 cups of low-sodium chicken broth and add a 15-ounce can of fire-roasted diced tomatoes along with 1 bay leaf. Bring to boil, then simmer for about 1 hour.

In the last 6 minutes, add 1 pound of peeled and deveined medium shrimp and stir gently until shrimp are cooked through.

Remove the bay leaf, taste, and adjust seasoning. Serve over cooked white rice and garnish with sliced scallions.