Go Back
Creamy and comforting green bean casserole with potatoes, showcasing the ultimate Thanksgiving side dish.
Lady Maria

Ultimate Green Bean Potato Casserole

This Ultimate Green Bean Potato Casserole elevates the classic dish with tender potatoes, creating a creamy and comforting side perfect for holidays or any special occasion. The addition of potatoes adds heartiness, texture, and a subtle sweetness that complements the savory mushroom sauce and crisp green beans.
Print Recipe Pin Recipe
Prep Time 25 minutes
Cook Time 30 minutes
Total Time 55 minutes
Servings: 6
Course: Side Dish
Cuisine: American
Calories: 350
Ingredients Equipment Method Notes

Ingredients
  

  • 1 1/2 pounds fresh green beans, trimmed
  • 1 1/2 pounds Yukon Gold or Russet potatoes, peeled and cubed
  • 1/2 cup milk
  • 1/2 cup sour cream
  • 1 tablespoon soy sauce
  • 1/2 teaspoon black pepper
  • 1/2 teaspoon garlic powder
  • 1/2 teaspoon onion powder
  • 2 tablespoons butter
  • 2 tablespoons all-purpose flour
  • 8 ounces mushrooms, sliced
  • 1/2 medium onion, chopped
  • 1 tablespoon vegetable oil
  • 1/2 teaspoon salt optional, to taste

Equipment

  • 9x13 inch baking dish
  • Cooking spray
  • Large Pot
  • Colander
  • Ice bath (bowl with ice and water)
  • large skillet
  • whisk
  • Mixing spoon or spatula
  • measuring cups and spoons
  • Oven

Method
 

  1. Preheat your oven to 350°F (175°C). Prepare a 9x13 inch baking dish with cooking spray.
  2. Bring a large pot of salted water to a boil. Add the green beans and cook for 3-4 minutes, or until they are bright green and slightly tender-crisp.
  3. Immediately transfer the blanched green beans to an ice bath (a bowl filled with ice and water).
  4. Once the green beans are cool, drain them well and set them aside.
  5. Place the cubed potatoes in a large pot and cover with cold water. Bring to a boil and cook for 10-12 minutes, or until they are fork-tender.
  6. Drain the cooked potatoes well and set them aside to cool slightly.
  7. Heat the vegetable oil in a large skillet over medium heat. Add the chopped onion and cook until softened, about 5 minutes.
  8. Add the sliced mushrooms to the skillet and cook until they are tender and have released their moisture, about 7-10 minutes. The mushrooms should be a beautiful golden brown.
  9. Melt the butter in the skillet with the mushrooms and onions. Sprinkle in the flour and cook for 1-2 minutes, stirring constantly, until the roux is smooth and bubbly.
  10. Gradually whisk in the cream of mushroom soup, milk, and sour cream. Stir until smooth and heated through. The sauce should be creamy and thick.
  11. Stir in the soy sauce, black pepper, garlic powder, and onion powder. Taste and adjust seasonings as needed. Add salt to taste if desired.
  12. In the prepared baking dish, combine the blanched green beans, cooked potatoes, and the creamy mushroom sauce. Stir gently to coat everything evenly.
  13. Sprinkle about half of the French fried onions over the top of the casserole. Save the remaining onions for later.
  14. Bake in the preheated oven for 20-25 minutes, or until the casserole is bubbly and heated through.
  15. Remove the casserole from the oven and sprinkle the remaining French fried onions over the top.
  16. If you want the onions to be extra crispy and golden brown, broil the casserole for 1-2 minutes, watching it closely to prevent burning.
  17. Let the casserole rest for a few minutes before serving. This allows the flavors to meld together and the sauce to thicken slightly.
  18. Serve hot and enjoy.

Notes

For best results, use Yukon Gold potatoes for their creamy texture. Avoid overcooking the green beans; blanching them briefly ensures they remain crisp-tender. To prevent the French fried onions from becoming soggy, add half before baking and the remaining half just before serving. The casserole can be assembled up to 24 hours in advance; add the second half of French fried onions right before baking. Store leftovers in an airtight container in the refrigerator for up to 3-4 days. Reheat in the oven at 350°F (175°C) for 15-20 minutes, covered with foil, or microwave individual portions.