Some of the holiday dishes can be made ahead and this Green Bean Casserole recipe is definitely one that works well being made a day or two ahead and still be full of crunch and fresh flavors.
You could prep the mushroom and sauce portions two days ahead and refrigerate making prepping this a breeze on the day. Or you could make the entire dish except for that topping a whole day ahead and heat in your oven with the toppings just before serving.
This entire dish relies on homemade meaning you control every ingredient and element in it and that means if you like a different hardy herb, toss that in or double the mushrooms if you want it to be super mushroom heavy, work to your palate and this will still be a stellar dish!
Why you'll love this
Easy prep
Overall, despite homemaking the béchamel and roasting the mushrooms, this is still pretty low on prep when you consider you're making the entire dish from scratch.
Fresh bean flavor
Despite cooking the beans and tossing with all the flavors together, the crunchy fresh green beans will still have a strong and perfect crunch that we love with our beans.
How to prepare Green Bean Casserole
- Roast em: Roast your mushrooms and garlic.
- Blanche your beans: Blanche em until lightly cooked.
- Béch-a-mel: Make your béchamel.
- Toss: Toss the beans, mushrooms and béchamel together in your baking dish.
- Cover and bake: Cover your baking dish with aluminum foil and bake.
- Finish: Remove the foil, toss over the onions and cheese and bake until golden.
- Serve up: Serve up and dig in!
Tips for the best Green Bean Casserole
Homemade crispy onions: Shallots are best here and for the quantity you need in this recipe, you’ll want to peel 2 large shallots and slice into half moons.
Pour 1 cup neutral oil (sunflower is best) into a small saucepan on medium high heat until you see ripples across the oil.
Toss in 1 handful of the onions where they should be simmering in the oil and stir to cook evenly for 1 ½ - 2 minutes until lightly golden.
Remove and place on paper towels to drain.
Repeat with the remaining shallots in handfuls until all are crispy.
These are best covered and consumed within 1 day of being made.
Make ahead elements of this dish: You can absolutely oven roast the mushrooms 2-3 days ahead of assembling, simply cover and refrigerate until you need them.
More side recipes you’ll enjoy
Roasted Green Beans with Sundried Tomatoes
Stoemp - Belgian Mashed Potato

How to make Green Bean Casserole:
Preheat the oven to 220C/425F and toss the mushrooms and garlic into a baking dish.
Place in the oven until the water runs out and they are brown, approximately 15 minutes with tossing every 5 minutes to ensure even cooking.
Remove and set aside.
Meanwhile, place a heavy saucepan on high heat and fill with enough water to blanche your green beans and add 2 teaspoons salt.
Once it has reached a rolling simmer, toss in a handful of green beans for 1 ½ minutes until green and ever so slightly soft.
Remove and drain and place into your baking dish.
Meanwhile, to make the béchamel, place the butter in a small saucepan on low heat and add in the flour.
Whisk until smooth and no dry portions remain on the edges.
Add in ¼ of the milk and whisk until fully combined and smooth.
Cook until thickened and lightly simmering, repeat with a further ¼ of the milk in batches until thickened and a sauce that still runs freely off your whisk.
Add in the mustard and dried rosemary and stir to combine.
Toss the garlic mushrooms over your green beans and pour over the béchamel over the entire baking dish.
Toss to coat everything evenly and cover with aluminum foil.
Bake for 20 minutes, remove the foil and sprinkle over the crispy onions and grated parmesan and return to the oven for 5 minutes.
Remove and allow to cool for 5 minutes before serving.
Dig in!

Green Bean Casserole
- Prep Time: 30 minutes
- Cook Time: 25 minutes
- Total Time: 55 minutes
- Yield: Serves 6
- Category: Sides
- Cuisine: American
- Diet: Vegetarian
Description
This Green Bean Casserole takes fresh green beans and tosses with oven roasted mushrooms and béchamel for an easy green bean casserole that is full of homemade flavor.
Ingredients
Mushrooms
250 grams / ½ pound button or brown mushrooms, sliced
4 garlic cloves, peeled and finely sliced
Béchamel
35 grams / 2 ½ tablespoons butter
35 grams / 4 tablespoons plain flour
1 teaspoon salt
350 milliliters / 1 ½ cups milk
½ teaspoon American mustard
1 tablespoon dried rosemary
Green beans
700 grams / 1 ½ pounds fresh green beans, trimmed
⅓ cup crispy onions (to homemake them, see notes)
22 grams / ¼ cup parmesan, grated
Instructions
Mushrooms
- Preheat the oven to 220C/425F and toss the mushrooms and garlic into a baking dish.
- Place in the oven until the water runs out and they are brown, approximately 15 minutes with tossing every 5 minutes to ensure even cooking.
- Remove and set aside.
Green beans
- Meanwhile, place a heavy saucepan on high heat and fill with enough water to blanche your green beans and add 2 teaspoons salt.
- Once it has reached a rolling simmer, toss in a handful of green beans for 1 ½ minutes until green and ever so slightly soft.
- Remove and drain and place into your baking dish.
Béchamel
- Meanwhile, to make the béchamel, place the butter in a small saucepan on low heat and add in the flour.
- Whisk until smooth and no dry portions remain on the edges.
- Add in ¼ of the milk and whisk until fully combined and smooth.
- Cook until thickened and lightly simmering, repeat with a further ¼ of the milk in batches until thickened and a sauce that still runs freely off your whisk.
- Add in the mustard and dried rosemary and stir to combine.
- Toss the garlic mushrooms over your green beans and pour over the béchamel over the entire baking dish.
- Toss to coat everything evenly and cover with aluminum foil.
- Bake for 20 minutes, remove the foil and sprinkle over the crispy onions and grated parmesan and return to the oven for 5 minutes.
- Remove and allow to cool for 5 minutes before serving.
- Dig in!
Notes
Homemade crispy onions: Shallots are best here and for the quantity you need in this recipe, you’ll want to peel 2 large shallots and slice into half moons.
Pour 1 cup neutral oil (sunflower is best) into a small saucepan on medium high heat until you see ripples across the oil.
Toss in 1 handful of the onions where they should be simmering in the oil and stir to cook evenly for 1 ½ - 2 minutes until lightly golden.
Remove and place on paper towels to drain.
Repeat with the remaining shallots in handfuls until all are crispy.
These are best covered and consumed within 1 day of being made.
Make ahead elements of this dish: You can absolutely oven roast the mushrooms 2-3 days ahead of assembling, simply cover and refrigerate until you need them.
Recipe by Roamingtaste
Nutrition
- Calories: 174 calories per serve
Keywords: sides, vegetables
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