Boil green beans for 4-5 mins. Plunge in iced water. Drain and set aside. Refrigerate for later use.
Sauté bacon till crispy. Add onions, garlic; cook till wilted. Add mushrooms; sauté for 5-6 mins. Set aside.
Butter skillet, whisk in flour. Cook for a minute. Slowly add chicken broth and milk, avoiding lumps. Simmer till thick.
Add cheese to the sauce. Mix well. Return mushroom mix to the skillet. Season with salt, pepper, and creole seasoning.