1. Preheat your oven to 350°F (175°C) and lightly grease a 9×13-inch casserole dish. When I was learning to cook alongside Mama Lu, she always said, “A well-prepped pan is the first step to a good meal.”
2. Bring a large pot of salted water to a boil. Add the green beans and blanch them for about 3-4 minutes until they’re bright green and slightly tender but still crisp. Drain and set aside. This step keeps them from turning mushy in the oven — a trick Mama Lu swore by.
3. In a large skillet, heat olive oil or butter over medium heat. Add the chopped onion and cook until translucent, about 5 minutes. Toss in the garlic and mushrooms, cooking for another 3 minutes until fragrant and soft.
4. Add the ground beef to the skillet. Break it up with a wooden spoon and cook until browned and cooked through, about 8-10 minutes. Drain any excess fat if necessary.
5. Stir in Worcestershire sauce, salt, and pepper to taste, then pour in the cream of mushroom soup and milk. Stir well to combine and let it simmer for 2-3 minutes until the sauce thickens slightly.
6. Remove the skillet from heat. Gently fold in the blanched green beans and half of the shredded cheese.
7. Pour the mixture into your prepared casserole dish, spreading it evenly. Sprinkle the remaining cheese on top, then scatter the crispy fried onions over everything.
8. Bake in the preheated oven for 20-25 minutes, until the cheese is bubbly and golden and the onions are crisped just right. The aroma will fill your kitchen with that unmistakable feeling of home.
9. Remove from the oven and let it rest for 5 minutes before serving. This little pause lets the flavors settle and makes it easier to scoop out perfect portions.

When I first made this casserole in my Portland kitchen, I thought about how Mama Lu never measured, just felt the rhythm of the cooking. This recipe gives you those guidelines but encourages you to trust your instincts — a pinch more salt, a handful more onions, whatever feels right to your taste buds.