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Green Beans with Mushrooms Onions and Mornay Sauce
Prep Time
10 mins
Cook Time
30 mins
Total Time
40 mins

These Green Beans with Mushrooms, Onions and Mornay Sauce is a classic, homemade side dish that's just perfect for the holidays ahead. Nothing canned here. It's a quick and easy, fresh from scratch side that everyone is guaranteed to enjoy!

Course: Side Dish
Cuisine: American
Keyword: green beans, holidays, mornay sauce, mushrooms, onions, Thanksgiving
Servings: 8 servings
Calories: 226 kcal
Author: MaryAnn Dwyer
  • 2 lbs. green beans, stemmed
  • 3 Tbsp. butter, divided
  • 1 large yellow onion, sliced and roughly chopped
  • salt and pepper, to taste
  • 1 Tbsp. olive oil
  • 1/2 lb. shiitake mushrooms, sliced
  • 1 1/2 cups cheddar mornay sauce
Cheddar Mornay Sauce
  • 2 Tbsp. butter
  • 1 shallot, finely chopped
  • 2 small garlic cloves, minced
  • 1 bay leaf
  • 2 thyme sprigs
  • 3 Tbsp. all-purpose flour
  • 1 3/4 cups milk
  • 1/4 cup white wine
  • salt and pepper, to taste
  • pinch of nutmeg
  • 1/2 cup shredded white cheddar cheese
  1. Fill a large pot with water. Add one teaspoon salt. Bring to a boil. Fill a large bowl with ice water. Add the green beans to the boiling water. Cook for 2 minutes (1-2 minutes longer if you like your beans less crunchy). Transfer beans to the ice bath. Drain beans and cut larger beans into thirds, smaller beans in half. Set aside.

  2. Add one tablespoon butter to a large skillet over high heat. Add the onions and season with salt and pepper. Cook for 2 minutes, until just lightly browned. Reduce the heat to medium-low and continue to cook the onions for 15 minutes, stirring often. Remove the onions from the skillet and set aside.

  3. Return the skillet to medium-high heat and add another tablespoon butter and the olive oil. Add the mushrooms and saute for 2 minutes. Season with salt and pepper. Once the mushrooms are cooked though and lightly browned stir in the caramelized onions and then remove from the skillet and set aside.

  4. Add the remaining tablespoon of butter to the skillet and cook over medium-high heat. Saute the green beans. Season with salt and pepper. Ladle the mornay sauce onto a large platter, top with green beans followed by the mushroom and onion mixture. Serve immediately.

White Cheddar Mornay Sauce
  1. In a small sauce pan, melt butter over medium heat. Add the shallots, garlic, bay leaf and thyme sprigs. Cook for two minutes, then discard bay leaf and thyme sprigs. Add flour and cook, whisking constantly for 3 minutes. Slowly whisk in the milk increasing the heat to medium-high. Cook until mixture starts to thicken, stirring frequently. Stir in the wine, reduce the heat to low and continue to cook for 3-4 minutes. Season with salt, pepper and nutmeg. Remove from the heat and stir in the cheese until smooth. Keep warm on your stovetop until you're ready to top with the beans and mushroom and onion mixture.

Recipe Notes

The recipe mentions that you can use oyster, shiitake or cremini mushrooms. I chose shiitake for today's recipe, but I've also made this dish with baby bella mushrooms.

You'll add your green beans to a pot of boiling water and cook them for about two minutes which will leave the beans nice and crunchy. If you like your beans a bit softer, cook for an additional minute or two.

Nutrition Facts
Green Beans with Mushrooms Onions and Mornay Sauce
Amount Per Serving
Calories 226 Calories from Fat 126
% Daily Value*
Fat 14g22%
Saturated Fat 8g50%
Trans Fat 1g
Polyunsaturated Fat 1g
Monounsaturated Fat 4g
Cholesterol 33mg11%
Sodium 144mg6%
Potassium 459mg13%
Carbohydrates 20g7%
Fiber 4g17%
Sugar 8g9%
Protein 7g14%
Vitamin A 1184IU24%
Vitamin C 16mg19%
Calcium 165mg17%
Iron 2mg11%
* Percent Daily Values are based on a 2000 calorie diet.