Begin by preheating your oven to 350°F (175°C). While it warms, bring a large pot of generously salted water to a rolling boil. This is where our green beans will get their first taste of seasoning.
Blanch the green beans in the boiling water for exactly 5 minutes. They should emerge bright green and crisp-tender. Immediately plunge them into an ice bath to halt the cooking process. This crucial step ensures your beans maintain their vibrant color and perfect texture.
In a large mixing bowl, whisk together. the cream of mushroom soup, milk, garlic powder, black pepper, salt, and Worcestershire. sauce until smooth. The Worcestershire adds a subtle umami depth that elevates the entire dish.
Drain the green beans thoroughly and pat them dry with paper towels. Any excess water will dilute our carefully crafted sauce. Fold the beans into the mushroom mixture, ensuring each bean is evenly coated.
Transfer the mixture to a 9x13-inch baking dish. Take a moment to spread everything. evenly—this ensures consistent cooking and serving portions.
Cover the dish tightly with aluminum foil and bake for 25 minutes. The covered baking allows. the flavors to meld while protecting our sauce from reducing too much.
Remove the foil and top with French-fried onions and Parmesan cheese if using. Return to the oven, uncovered, for an additional. 10 minutes until the onions are golden brown and crispy.