Cajun Green Bean Casserole

Name: Cajun Green Bean Casserole
Ingredients: 1 1/2 tsp. kosher salt, plus more for the water; 2 lb. green beans, ends trimmed, halved crosswise; tbsp. plus 1 teaspoon olive oil; 4 strips bacon, chopped; 3 garlic cloves, chopped; 2 stalks celery, chopped; 1 small onion, chopped; 1 small red bell pepper, chopped; 1 tbsp. plus 1 teaspoon Cajun seasoning; 4 tbsp. salted butter; 1/4 c. all-purpose flour; 2 1/2 c. whole milk; 1/2 c. half-and-half; 2 tsp. hot sauce; 2 2.8-oz. cans crispy fried onions (about 3 cups)