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Green Bean Casserole Stuffed Mushrooms

  • Author: Tessa
  • Total Time: 25 mins
  • Yield: 24 - 30 mushrooms 1x


The ultimate holiday side dish turned appetizer! Green bean casserole stuffed mushrooms will satisfy your comfort food craving without leaving you over stuffed before a big meal.


  • 20 oz. medium button mushrooms, with stems
  • Olive oil cooking spray (or extra vegetable oil)
  • 1 T vegetable oil or butter
  • 10 oz. pkg. frozen green beens, chopped into 1/4” pieces
  • Salt
  • Ground black and/or white pepper
  • 1 1/2 T butter
  • 1 medium shallot, chopped small (1/3 C)
  • 1 1/2 T all-purpose flour
  • 1/4 t mustard powder
  • 1 1/2 C whole milk
  • 1/2 C finely grated parmesan cheese
  • 1/8 t paprika
  • 2 T chopped parsley, plus more for garnish
  • 1/3 C packaged French fried onions (or the fried shallots from this recipe), roughly chopped


  1. Preheat the oven broiler and move rack about six inches from heat. Wipe the mushrooms clean and pop out the stems, using a paring knife to remove any stem stuck in the cap. Chop stems small and set aside. Place caps dome up on a nonstick (or lightly oiled) rimmed baking sheet. Spray or brush tops with oil and sprinkle with pepper. Broil about 5 minutes, until caps just begin to soften and release a little liquid. Set oven to 375 and set mushrooms aside.
  2. Heat butter or vegetable oil in a 10 inch skillet over medium heat. Add mushroom stems and sauté, stirring infrequently, until browned and tender, 7 to 10 minutes. Scoop out of the skillet and into a mixing bowl, leaving extra oil in the skillet. If no oil remains, add 1/2 tablespoon. Raise heat to medium high and add frozen beans. Cook until tender and any water has evaporated, about 5 to 10 minutes. Add to bowl with the mushroom stems. Carefully wipe out skillet with a damp cloth.
  3. Heat milk until warm, about 2 minutes in the microwave at 50% power. Melt butter in the skillet over medium low, then add shallots. Cook a few minutes, until tender but not browned, then sprinkle flour and mustard powder into the pan. Stir constantly for 2 to 3 minutes, until flour is no longer grainy and has darkened slightly. Reduce heat to low, then slowly whisk in milk. Raise heat gradually to bring to a simmer while whisking. Adjust heat to maintain a gentle simmer, stirring frequently, until thickened, about 5 minutes. Off heat, stir in 1/3 cup of the parmesan, 3/4 teaspoon salt, 1/2 teaspoon white pepper (a little more if using black), paprika, and parsley. Adjust salt and pepper to taste.
  4. Turn the mushroom caps face up. Mix half the sauce with the bean mixture. Pile into the mushroom caps, packing it into a mound. Bake for 15 minutes, until mushrooms are juicy and tender. Mix remaining parmesan with the fried onions. Remove tray from oven, sprinkle mushrooms with fried onion mixture, and bake or broil another few minutes, until browned. Cool slightly before sprinkling with more parsley and serving warm.


Substitute an equal quantity of fresh blanched or drained canned green beans for the frozen beans.

Extra white sauce keeps well in the refrigerator or freezer. If you have extra green bean casserole mixture, bake it in a lightly greased ramekin at 375 until hot and bubbly!

  • Cook Time: 25 mins
  • Category: Appetizer
  • Cuisine: Comfort Food