In a large skillet, heat the vegetable oil over medium heat. Add the sliced andouille sausage and cook until browned, about 5 minutes.

Add the diced onion, green bell pepper, and celery to the skillet. Sauté until the vegetables are soft, about 5-7 minutes.

Sprinkle the flour over the sausage and vegetable mixture, stirring constantly for about 2 minutes to create a roux.

Slowly pour in the chicken broth and heavy cream, stirring continuously to avoid lumps. Bring to a simmer.

Add the Cajun seasoning, black pepper, and salt. Let the gravy simmer for about 15 minutes, stirring occasionally, until it thickens.

Serve the andouille sausage Cajun gravy over rice or biscuits.