Classic Gumbo with Andouille Sausage & Shrimp (with Video)

Ingredients

• 7 tablespoons vegetable oil, (divided)
• 1½ pounds smoked Andouille sausage ((see note))
• ¾ cup all-purpose flour
• 1½ cups chopped yellow onions, (from one large onion)
• 2 stalks celery, (diced)
• 1 red bell pepper, (seeded and diced)
• 7 cups low-sodium chicken broth
• 2 tablespoons tomato paste
• 1 teaspoon salt
• 1 teaspoon sugar
• ¼ teaspoon cayenne pepper ((optional))
• 2½ teaspoons Creole seasoning, (such as Emeril's Essence or Tony Cachere's)
• 1 teaspoon chopped fresh thyme (or ½ teaspoon dried)
• 2 bay leaves
• 1½ pounds large shrimp, (peeled and deveined)
• ½ cup chopped scallions, white and green parts, (from about 4 scallions)
• Cooked white rice, (for serving)